Getting a price to replace my 21 year old WaterFurnace GeoHP

[woodgeek]

If they made a HPHW with a plastic tank, I probably would get rid of my Marathon and buy that. I plan on tying a Geyser into my system one of these days when I have some extra $$$ to throw around.

Scott

I think you will be waiting a while on the plastic HPWH....with a low temp working fluid, you need a large area of good thermal conductivity. I suppose they could put a coil inside the tank, rather than wrapping it around, as they do with the current all in ones.

Personally, I have not seen an external HP system with stated EF factors as high as the current (2nd gen) all in one units. There seems to be a big skew in this board towards the externals....but they seem to have lower eff IMO.

Don't know about the geosprings, but my all in one has an active anode rod, rather than a sacrificial one, I would not be surprised if it lasted as long as a Marathon, or at least until the compressor is shot.

EDIT: geosprings have a 'heavy-duty' sacrificial anode rod that is compatible with the 10 yr tank warranty.

 

[sloeffle]

Personally, I have not seen an external HP system with stated EF factors as high as the current (2nd gen) all in one units. There seems to be a big skew in this board towards the externals....but they seem to have lower eff IMO.

No to go too far off topic.

The external HP would have a dual role in my situation. It would make hot water and act as a dehumidifier in my basement. I talked to Tom in Maine about getting one and he thinks it would be over kill since I already have a DSH on my geo. Wiring it up to not run when the geo is running would be another problem.

My Marathon is only three years old so I don't think I will be getting a traditional HPWH anytime soon.

Don't know about the geosprings, but my all in one has an active anode rod, rather than a sacrificial one, I would not be surprised if it lasted as long as a Marathon, or at least until the compressor is shot.

Can you explain the difference ? I did some quick googling and couldn't really find a definition of an active anode rod.

 

[woodgeek]

Sorry, 'powered anode' is the preferred term.

A sacrificial anode has an electrochemical reaction on its surface that generates a small voltage on the rod, and it is that voltage to prevents galvanic attack at the tank liner. This reaction, however, consumes the anode slowly, like a big battery. When it is gone the tanks rusts out. As you know, the major difference b/w a 5 year tank and 10 year tank is the size of the anode rod. Replacing the anode regularly will often make even cheap tanks last a long time.

With a powered anode, a rod of non-reactive, non-corroding metal is suspended in the tank, and a small voltage and current is applied to it using a small external power supply, powered by grid power. Its galvanic effect is precisely the same vis-a-vis preventing tank corrosion, but it does not get consumed, nor does it add metal ions or other gunk to your water supply. It is permanent.

The only downside is that tank corrosion can occur during grid outages. Also, just switching off the breaker during vacation will also lead to a couple weeks of tank corrosion. Instead, these units have a 'vacation mode' that turns off the entire unit except the rod power supply.

 

[Jerry_NJ]

How is your water furnace Envision DSH set up, one tank or two? Seems when the HP is running you may be getting enough hot water from the DSH, correct?

My question is skip the DSH and put in just a HP WH, or skip the HP WH and put in a DSH with just one 80 gallon dual element water heater with the lower element off, and maybe with a timer that shuts down the water heater all together for many hours a day/nigh when I expect to see low to no use. I am not considering installing a dual tank system... albeit I like the dehumidification benefits of the HP WH.

I am also considering not buying the emergency heat but would still like to have a 2kw AUX heating element.

 

[sloeffle]

With a powered anode, a rod of non-reactive, non-corroding metal is suspended in the tank, and a small voltage and current is applied to it using a small external power supply, powered by grid power. Its galvanic effect is precisely the same vis-a-vis preventing tank corrosion, but it does not get consumed, nor does it add metal ions or other gunk to your water supply. It is permanent.

Glad to hear that the hot water heater manufacturers have finally gotten into the 21st century. Personally, I never understood why you would build a tank that holds water out of steel. I saw my folks have two broken hot water heaters in 20 years and that sold me on the Marathon.

How is your water furnace Envision DSH set up, one tank or two? Seems when the HP is running you may be getting enough hot water from the DSH, correct?

My question is skip the DSH and put in just a HP WH, or skip the HP WH and put in a DSH with just one 80 gallon dual element water heater with the lower element off, and maybe with a timer that shuts down the water heater all together for many hours a day/nigh when I expect to see low to no use. I am not considering installing a dual tank system... albeit I like the dehumidification benefits of the HP WH.

One 50 gallon tank. Only three occupants in my house.I have it setup like the diagram in this link. As I stated before, shutting off the bottom element will result in lukewarm water. The DSH will only run when the furnace is running. If you have a mild summer like we had this year then you are not going to make much "free hot water". The DSH stops making water when the water temp reaches 130F. Per Waterfurnace doco:

Hot Water High Limit
(Domestic Hot Water Option)
This mode occurs when the hot water input temperature is at
or above 130°F for 30 continuous seconds. The DHW limit status
LED on the unit illuminates and the hot water pump de-energizes.
Hot water pump operations resume on the next compressor cycle
or after 15 minutes of continuous compressor operation during the
current thermostat demand cycle

I think we have beat this to death enough. But I think you are money ahead forgoing the DSH and getting a HPHW.

 

[Jerry_NJ]

Thanks, 130 degrees is fine with me, we run the hot water heater at 125 degrees now. I understand I'm on resistive hot water during mild weather, I don't have to see a payoff of the DSH in the first couple of years. With the improved hook up to the new 80 gallon hot water heater I think the DSH will be a good investment. Still, I like the year around dehumidifcation from the HP HWH.

I sent my dealer a note via his web site asking him to price my system with model 38, 3 Ton, in place of the model 49, 4 Ton (that should shave a few bucks off) and with no emergency heat, another option I have found of almost no use in my 21 years experience. First, I had the resistive heaters disconnected much of the time so I could turn down the heat about 5 degrees at night and not get whacked with Aux/Emer heat thrown in when I ask the HP to bring the house back up in the morning. At least 99% of the times I needed emergency heat (recall one 5 day and one 10 day stretch) it was because electricity was out... not emergency heat, then once for a few days when the blower went out (at about year 15) well no resistive heat without a blower. Too, I have at least 5 KW of emergency heat in portable units, and an airtight wood stove (insert). The insert is what allowed me to stay in my home when the electricity went out, and when the blower went out. I think these two cuts from the proposal should knock at least another $1K off the cost, really only $700 given the rebate I'll not be getting for options not purchased. That's about enough to pay for the DSH.

 

[moey]

Can you use your resistive heating elements from your existing system? Depends on the size I guess. Id be hesitant not to get something in case your HP locks out for some reason while your out of town.

 

[woodgeek]

I was pricing out 10kW strips yesterday....$60. And presumably the $$ wiring is already there, just kill 'em at the breaker if you don't want them to ever come on.

 

[Jerry_NJ]

I can ask my installer/dealer. He agreed to use my existing loop pumps (in my current system it ran one pump for Stage I and two pumps for Stage II, dealers says that's no longer the practice. Both pump motors were replaced about two years ago and considerable $$ by another dealer I no longer use. But that's another story.

In any case he seems to be okay with reuse, but the subject reuse of the Aux/Emer heating strips didn't come. I did ask about cost in the context of not installing the heating strips. If I go for the smaller 3 Ton (or 3.5 Ton I think he calls it) the model says I need a few hours of at least 2KW aux heat at a 12 degree outside temperature. It gets that low in NJ, but only for a few hours in the wee hours of the morning.. when I'd like to set the house temp down to 65 degrees, not the design 70 degrees. Still, I think I recall (couldn't be more than a few times, I really don't remember when) a couple of times NJ saw zero degrees, which says the small HP would have to have aux supplements... but I can use my wood stove and portable heaters too... HP just needs a "little" help.

Talked today via telephone and the dealer still recommends going with the 4 Ton unit, saying that the smaller unit is only a few hundred less expensive. And, the "design maximum balance point is 13.5 degrees" where as the 4 Ton has a "..max balance point of 0 degrees" which I think is overkill.

Again I'm more concerned about too much cooling in the 4 Ton not too little heating in the 3/3.5 Ton.

From the Water Furnace GeoLink Project Report it shows a lot 100% run time on the smaller unit, starting at 12 degrees, and as noted it can't handle 11 degrees if I want 70 degrees inside. Not a big deal to me for all the above reasons, and the resistive aux will run to handle that at the cost of a few dollars a year for the NJ weather model. I think this is good, right, the HP: compressor, blower, and loop pumps all like running continuously more that cycling between Stage I and Stage II.

Here's a strange number in the GeoLink numbers. It shows the smaller unit with an average COP of 3.78 seems rather low given the Stage II is rated at 4.1 and that excludes Aux (resistive) heat which is accounted for elsewhere in the report. And, the HP runs a lot in Stage I too and that has a COP of 4.8 how can the "average COP" be so low? To complete the picture the COP is specified at a loop temperature of 32 degrees, the Report shows the "Minimum Extreme Tempeature" at 37 degrees and the average heating loop temperature at 45 degrees. Something just doesn't add up, that is I think the HP should be performing better than the model shows. Similar remarks for the model run on the 4 Ton unit. Lower average COP 3.27 with specs at 4.0 and 4.6 for 32 degree loop temperature.

I may push for the smaller unit, not sure if I want to ask about the question in the above paragraph. There seems to be no reason Water Furnace would run a model that shows lower HP performance than they claim in the specifications. Surely the specifications are verified by tests, at least in the design check-out and perhaps in the qualification for Energy Star ratings.

 

[woodgeek]

You don't want to hear it, but here is goes....

1) If the balance point were 12 degrees (at 70°F inside), you are correct that you would not need aux at 65°F overnight inside....BUT, you would not be able to recover the heat w/o aux. It would go to 100% and take many hours to climb out from 65 to 70. I suppose you would need the woodstove.

2) I would worry more about the error on the 12°. It is prob 12±5 or 12±10°F. What if the installer is wrong, and the balance point is 22°F? And you have no aux! You'd be calling him back. He is pushing the 4 ton to avoid that possibility...the dreaded callback and unhappy customer.

3) The real COP of geos in the field as measured in surveys is closer to 3-3.5, not including any aux calls. The manufacturers do not include the pump energy, or might use a real low-ball estimate for pump energy. Installers hate call-backs, so they always go for a big beefy pump that uses a ton of electricity compared to manufacturer assumptions. Add in too small loops, or too restrictive loops, and you get cold loop temps, even more pump energy, etc. It's sad, but you really can't trust the COP numbers from geo manufacturers. If you want to know your COP, you need to put a sub-meter on the power in, and do some calorimetry on the BTU output.

4) The aux strips are just coils of nichrome wire like in a toaster or hairdryer. The cost of a 2 kW or 5 kW or 10 kW are all going to be in the $50-100 range for the hardware. A rather expensive part of your install is the heavy gauge copper running from your box to the geo/aux.... and obviously all that wiring is going to be reused. The run cost of the aux will not depend on its size. If you need XXX extra BTUs, the stat will either call the little aux for long time, or the big one for a short period, same kWh and $$. So, just get a decent sized one for the functionality....like 5 or 8 or 10 kW, it won't cost much with the wiring in place. And then switch the breaker off for it if you want, and rely on the wood insert. But when you sell you have an actual normal system installed, and a decent back-up.

 

[Jerry_NJ]

Yes, I given up on not buying resistive heating (haven't asked about reuse, but the cost of new isn't a deal breaker). This is a replacement of an existing unit that has dual 5KW (approx) heating strips, so the brakers are there and usable.

Well the GeoLink program must take the other electrical loads into account, thus the smaller COP numbers in the run. If the model is correct it show my house design load (at balance point?) is 46 KBTU for both units, guess that's why the bigger unit crosses the Load Line at a lower temperature. In any case, the bigger unit maxes out at about 37KBTU the smaller at 28KBTU (with one 5K Resistive that goes up to about match the larger HP only), but the weather data predicts only 35 hours below 12 degrees. Further the model predicts the small unit will use a total of 107 KWH total resistive for the year. Thats about $15, not a problem and there is no question the smaller unit will do a better job of air conditioning, including humidity control.

So, I am again reaching the conclusion that the smaller unit is the right answer, with aux/emerg resistive included. The installer said he can set the aux to stay off for 30 minutes when more than 2 degrees are called for at the thermostat. I could be convinced to not turn the heat down at night, maybe just damper down the Master Bedroom ducts - still plenty of room to move air and the small unit moves less CFS too... guess the lower blower rate makes the temperature out about the same for both units. Here I believe the best HP is one that runs a lot at low power consumption - this does a better job of cleaning the air, and of distributing temperature to all corners of the house. The model sees the smaller unit running 100% in Stage II for about 1000 hours a year. That's a little over a month of constant running. Of course it comes in spurts with warmer outside temperatures in-between. Still, the smaller unit will see more constant run with fewer start/stop. Further I think the small unit can work with only one loop pump running for both Stage I and II, spec shows 8 gpm, the big unit needs 11 gpm in Stage II.

Yea your right on the "when I sell" very unlikely the buyer will be anything like me : ) or : ( either way I find my conservative (tight wad) thinking is well off normal. So it would be the responsible thing for me not to Screw up the next buy who had no idea the heating system needed so much hand support.. besides, he/she will likely have to go to work too, not retired. I used to travel a lot on business and my wife had to depend on the HP not on backup/aux arrangements. Still the small unit will work just fine needing and having only a minimal use of resistive axillary heat. With the 5 KW resistive on the little unit is putting out about 45KBTU with a combined COP of about 2.0, not a big deal give the small number of hours this will be needed.

 

[woodgeek]

Let's play with some load numbers. I would interpret his numbers as follows....

Usually, they start with a 99% temp, an outdoor temp a location is above 99% of the time (all but 80 hours on average). Sounds like your 99% temp is around 13°F (mine for comparison is 5°F).

You then compute the BTU load at the 99% temp, the 'design load' and make sure the unit can cover it. Sounds like your design load is 46 kBTU/h. Seems like a reasonable number (mine for comparison is 38 kBTU/h).

So, on the coldest days of the year ('design day'), the bigger unit will get 37 kBTU from the geo, and 9 kBTU (about 2.5 kW) from the aux. The smaller unit will get 28 kBTU from the geo, 18 kBTU (about 5 kW) from the aux. Times 24 hours, the larger unit will burn 2.5*24 = 60 kWh/day in the strip, while the smaller unit will use 2x that, 120 kWh/day. (for comparison, during the polar vortex, I ran my 15kW strips for 9 hours, in addition to my (low output) AHSP, burning 135 kWh/day)

My guess is that when you were still working, the old unit could've called 50 kWh on scattered really cold days and you would not have noticed on the bill.

Much more important (IMO) is performance at your 'average January temp'. Your bill will not be much affected by design day...you want to make sure than your **average** day does not use much aux. In other words, you want your balance point temp (where no aux is required) to be well below the January ave temp. My average Jan temp (24 hour ave) is ~29°F, but it seems you are a little warmer, I'd guess yours is 31°F. You can read it on your February electric bills, BTW.

Now for the fun part....if you need 46 kBTU at 12°F, how much do you need at 31°F? The DeltaT (indoor outdoor) is 39° instead of 58°F, so you would need 46*(39/58) = 31 kBTU/h. You can figure appliances and body heat and solar gain provide maybe 5 kBTU/s, so you would need 26 kBTU at 31°F. This seems very close to the Stage II output of the smaller unit. If this analysis is correct, the smaller unit's 'balance point' is very close to you ave Jan temps. If this is true, I would expect up to 10-15% of seasonal BTUS to come from aux (if you didn't burn wood), or it would raise your heating bill by 30-40% if you did not burn the insert, I suppose $200-300/year. The bigger unit has a balance point near 70°F - (37+5 kBTU* (58°F/46kBTU)) = 17°F, and you would run little aux, as previously reported.

So, the number your report suggest that your balance point for the two units is ~29°F for the smaller unit, or 17°F for the larger (and this is assuming 5 kBTUs from 'background sources to help). With the smaller unit, I think you are looking at $200-300 a year OR a lot of insert burning (most days) for the coldest 4-6 weeks of the year. The bigger unit....just what you have now, disconnect the strips, and fire up the insert during a few days a year, or pay the same bills you did last year.

Are you going to spend an extra $2k to get a DSH, after a bad experience with them before, and not spend enough to get a big enough compressor to cover your average January load to save a couple bucks on install??

I think you are having a 'forest-trees' problem...You are all about staging and pump usage and might be missing what the darn thing is for in the first place....space heating!

I'd go for the bigger geo myself, but it is of course your call.

Talk to your installer...I don't get this whole 'I didn't ask', why not? Ask HIM to explain it to you to your satisfaction! He can take 20-30 mins face to face to discuss options, expected outcomes etc.

For the record, I think you should ditch the DSH, and use the savings for a new GE geospring HPWH, the larger geo compressor, and 10 kW strips.

 

[sloeffle]

If you want to know your COP, you need to put a sub-meter on the power in, and do some calorimetry on the BTU output.

We have the 049 ( 4 ton ) unit and I put an amp clamp on one side of the 220 line coming into the unit and it was pulling 11 amps. So the whole unit ( pumps, DSH, compressor ) was pulling 22 amps total. My unit has two Grundfos pumps. They call it a Geolink Flow Center.

For the record, I think you should ditch the DSH, and use the savings for a new GE geospring HPWH, the larger geo compressor, and 10 kW strips.

woodgeek, I think you are spot on with your recommendation except for the GE HPHW. I have had back luck with their appliances in the past. Great write up on your last two posts BTW.

 

[woodgeek]

Fair enough. He could get a conventional (well insulated) electric tank (or keep the one he has now), and as two retirees their DHW usage will be so low that it will not cost much to operate.

I still suspect upsizing the compressor will be a smaller upcharge than the DSH, and the aux savings from it would be much greater than the projected DHW savings from the DSH. That is: a smaller geo+DSH is more expensive to buy and to operate than bigger geo+no DSH+existing elec tank.

The next owner can replace with a (more mature, cheaper) HPWH 8 years from now if he/she wants.

To the OP: if you are worried about dehumidification....don't. If you have a variable speed blower n the air-handler, ask the installer about slowing the blower in cooling relative to heating. At 300 cfm/ton versus the rule of thumb 400, you would get more dehumidification than you did before.

 

[sloeffle]

Fair enough. He could get a conventional (well insulated) electric tank (or keep the one he has now), and as two retirees their DHW usage will be so low that it will not cost much to operate.
I still suspect upsizing the compressor will be a smaller upcharge than the DSH, and the aux savings from it would be much greater than the projected DHW savings from the DSH. That is: a smaller geo+DSH is more expensive to buy and to operate than bigger geo+no DSH+existing elec tank.
The next owner can replace with a (more mature, cheaper) HPWH 8 years from now if he/she wants.

Should of been more clear on my last post.

No DSH. A HPHW is the way to go. Just not the GE flavor IMO.

 

[woodgeek]

Should of been more clear on my last post.

No DSH. A HPHW is the way to go. Just not the GE flavor IMO.

We think the same, but on a 5 year ownership horizon, with two retirees not using a lot of water, on a budget, and having an electric tank already (?), I could believe that the payback might not be there on an expensive, non-GE unit. I love my giant AOSmith, but the MSRP is $2k, as much as a DSH.

The OP needs a lot of space heat, but not much DHW. The Next Owner can upgrade the DHW if he/she wants to reap some savings.

 

[Jerry_NJ]

Seems my writing ability isn't up to the task.

I spoke with my dealer about the HP WH, he sells AO Smith, the price is high. We have already decided to reusing not only my ground loop, a given, but also my GeoLink Flow Center which had it two pumps replaced about two years ago. It pumps 6 GPM with one pump and 12 GPM with both. The 3 Ton would have "extra" flow in Stage II as it needs only 8 GPM. The plan is to always run both pumps, WF seems to have given up on using lower pumping rate for Stage I. I have not spoken with my dealer on reuse of my existing aux/emerg heat.

The Geoling Project report (a Water Furnace software package, or at least not the dealers private way) clearly states the for the 3 Ton unit
Balance point 13.5 degrees and Stage II heat goes 100% at 17 degrees, with no auxiliary heat until 12 degrees. It also states the annual heat is 99% HP 1% Resistive, at 107 KWH. It also shows the 3T unit annual cost to be over 13% lower cost, this includes heat/cool and hot water (assumes DSH).

I hope the above dispels any notion that I'd be screwing any buyer who doesn't want to use fire wood heating supplement. The bottom line on both uits is quite affordable, and assumes a higher electric rate than I am now paying: 3Ton Totals $1,423 and 4Ton $1,549 and both hold the house to the same heating/cooling demands. The only "ringer" that troubles my dealer about the smaller unit is the model assume an "internal heat gain" of 8,400 BTU/Hour, but even if it were zero the smaller unit appears to be able to handle heating all the way to 32 degrees, and surely most of the time below 32 degrees outside are after dark. The model says for my area: about 1,000 hours total. So the worse case suggests the 3Ton could use aux heat help 1,000 hours a year, at 8KBTU, 1,000 hours of 2.35KW per hour totals to 2,350 KWH at 15 cents costs $345 in a year. Well, obviously the true "internal heat gain" is more than zero, suppose it is only have the estimate, and is 4KBTU/Hour, the the above cost goes to half and makes the total cost about the same the 4Ton for heating, and the 3T still cost less for cooling and does a better job.

Further data favoring the 3T.
Loop flow for Stage II is 8 gph, gets 12 gph 4Ton requires 11 gph, also get 12
Stage I fan 1050 cfm, Stage II fan 1250 cfm, 4Ton much noisier at 1350 cfm and 1550 cfm respectively.

One thing not clear is the Project Report shows the DSH with a variable BTU output and it remains on at or greater than 1,302 BTU/H or greater throughout the temperature range, in the case of the 3T that includes even when some light aux heat is being used. The report also shows the DSH output as high as 3,014 BTU/H for the 3T and as high as 5,332 BTU/H with the 4 Ton, talking some serious water heating at the upper end. Strangely both units in the Report show low heating at the upper cooling load ranges, must be an assumption built in about the temperature of the water in the tank, i.e., when 97 degrees outside, the HP has been running at or near 100% and the tank is full of hot water. At the mid range when the HP is running below 20% we see the high input heat to the Water Heater - and they are different as shown, so the DSH must also reflect the size of the HP unit, not one DSH fits all. Thus, while the 3Ton runs a lot more the 4T produces more water. The Report (which you all seem to doubt) shows the 3Ton HP producing 55% of my hot water and the 4Ton producing 58%.

My one assumption that keeps me pushing for the 3Ton is the belief that long run times with fewer start/stop cycles is the best operation condition when using a heat pump (or any facility that uses rotating machinery).

 

[woodgeek]

For the record, if you and your installer are all agreed on what you want and what you will get, I really don't care.

The Geoling Project report (a Water Furnace software package, or at least not the dealers private way) clearly states the for the 3 Ton unit
Balance point 13.5 degrees and Stage II heat goes 100% at 17 degrees, with no auxiliary heat until 12 degrees. It also states the annual heat is 99% HP 1% Resistive, at 107 KWH. It also shows the 3T unit annual cost to be over 13% lower cost, this includes heat/cool and hot water (assumes DSH).

Ok, I'm sorry but this makes no sense to me. If we think the balance point is where the geo hits 100% and the aux starts cycling, then why does the report 3 different temps for that condition....12°F, 13.5°F and 17°F?

I hope the above dispels any notion that I'd be screwing any buyer who doesn't want to use fire wood heating supplement. The bottom line on both uits is quite affordable, and assumes a higher electric rate than I am now paying: 3Ton Totals $1,423 and 4Ton $1,549 and both hold the house to the same heating/cooling demands. The only "ringer" that troubles my dealer about the smaller unit is the model assume an "internal heat gain" of 8,400 BTU/Hour, but even if it were zero the smaller unit appears to be able to handle heating all the way to 32 degrees, and surely most of the time below 32 degrees outside are after dark. The model says for my area: about 1,000 hours total. So the worse case suggests the 3Ton could use aux heat help 1,000 hours a year, at 8KBTU, 1,000 hours of 2.35KW per hour totals to 2,350 KWH at 15 cents costs $345 in a year. Well, obviously the true "internal heat gain" is more than zero, suppose it is only have the estimate, and is 4KBTU/Hour, the the above cost goes to half and makes the total cost about the same the 4Ton for heating, and the 3T still cost less for cooling and does a better job.

Yeah. That's quite a 'ringer'. How does your house have a 8400 BTU/h internal gain? Your appliances and body heat are prob 3-5 kBTU/h tops. Maybe they are figuring on a lot of solar gain? The after dark thing is irrelevant. Yeah, it will keep up at reduced nighttime setpoint temps, but it won't be able to recover the indoor temps in the morning until a couple hours after the outdoor temp rises above 32°F, without aux or the insert. I've lived with a balance point in that range, setbacks, and no aux for a while....it all seems aok until you try to recover.

How does the 3 ton and 4 ton both hold the house to the same heating demands (without aux), when they have very different rated BTU outputs??

Now the balance point might be 32°F (close to my estimate), and you are paying up to $345/yr in aux. If we split the difference, and say you have 3-5 kBTU internal gain, and a 32°F balance point for the 3 ton (without gains), then sure, it might just cost you a $100-150/yr in extra aux (in an average year) than the 4 ton.

Further data favoring the 3T.
Loop flow for Stage II is 8 gph, gets 12 gph 4Ton requires 11 gph, also get 12
Stage I fan 1050 cfm, Stage II fan 1250 cfm, 4Ton much noisier at 1350 cfm and 1550 cfm respectively.

I don't see where giving the geo more gph than it needs is desirable....pump power is a major source of reduced COP. If you are going to run both pumps all the time for both units, the 4T will achieve a higher COP, by running the two pumps fewer hours. IF you think your air is too noisy, slow the fan down if you have variable speed, the effect on COP is quite modest.

One thing not clear is the Project Report shows the DSH with a variable BTU output and it remains on at or greater than 1,302 BTU/H or greater throughout the temperature range, in the case of the 3T that includes even when some light aux heat is being used. The report also shows the DSH output as high as 3,014 BTU/H for the 3T and as high as 5,332 BTU/H with the 4 Ton, talking some serious water heating at the upper end. Strangely both units in the Report show low heating at the upper cooling load ranges, must be an assumption built in about the temperature of the water in the tank, i.e., when 97 degrees outside, the HP has been running at or near 100% and the tank is full of hot water. At the mid range when the HP is running below 20% we see the high input heat to the Water Heater - and they are different as shown, so the DSH must also reflect the size of the HP unit, not one DSH fits all. Thus, while the 3Ton runs a lot more the 4T produces more water. The Report (which you all seem to doubt) shows the 3Ton HP producing 55% of my hot water and the 4Ton producing 58%.

Just for the record, if you used 100% resistive DHW, I suspect your annual bill would be ~$300. If a DSH is providing 50% for free, it is saving you $150/year. You said the DSH and second tank cost $2k. Why would you spend $2k for a system that saves you $750 over the next 5 years before you sell the place? A geospring HPWH costs $500 after rebates, with extended warranty, and it would also save you >50% of your hot water bill, $150/year. But its a no-go, despite paying for itself before you sell the house.

Seems you are very concerned about saving $150/yr on DHW, but not so concerned about paying an extra $150-250/yr on aux. I don't get it.

My one assumption that keeps me pushing for the 3Ton is the belief that long run times with fewer start/stop cycles is the best operation condition when using a heat pump (or any facility that uses rotating machinery).

We're gonna disagree on this one too. Certainly true for internal combustion engines with sliding metal-metal contacts whose oil film drains away. But I have NEVER heard of such a think for electric motors....all low temps, roller bearings, no combustion....why would it not want to start and stop??

 

[Jerry_NJ]

WG, you sure like to argue, but I guess that's why I came here, to get other views.

You have not persuaded me otherwise, and ask that you at least get the correct information on what is the biggest cause of wear on electric motors, start/stop. that's one reason for the upgrade to the EMC blower, and variable speed compressors (I am buying a two speed compressor with a EMC variable speed blower) - soft start up, gradual torque build, not just slam on/off. There is no doubt in my mind that the 3 Ton running for 24 hours straight suffers less wear than the 4 Ton going through a considerable number of cycles during the same 24 hour period going between Stage I and II, i.e., Stage II, then stop and restart in Stage I, then stop and restate in Stage II... and so on and just for a guess it may go through 10 or 20 cycles of switching between Stage I and II while the 3 Ton is running constantly in Stage II. The 4 Ton compressor is suffering considerable more damage.

The blower speeds are not just a pick one, these are the speeds Water Furnace recommends for the two units. Seems the 4 Ton moving more BTUs needs more air to do that to provide the design COP. I suspect the Plenum heat gain for both units is about the same, the 4T moves more heat my using more air. Both need the same temperature drop across the condenser to operate efficiently, so the 4T has to move more air. My current three speed blower is something like 1000 cfm (manual on mode runs when HP not operating) and it is almost silent. It runs 1200 cfm in Stage I and 1500 cfm in Stage II and is noticeable noise. One of the things I liked about the existing Geo HP, which replace a 6 year old GE air-to-air HP, was it is SO quiet, compared to the roar of the old AS HP. If the 3 Ton can do the job and be even quieter, great !

As for the temperatures, the WF Program based on inputs the installer 21 years ago provided to define my home and that established the 13.5 degree balance point for the 3 Ton and 0 degrees for the 4 Ton. I picked the other temps off of a table showing the energy uses at different temperatures, one being 12 degrees and one being 17 degrees.... the 17 degrees being the first time 100% run time is shown, 12 degrees (another data point) being the first time Aux heat is reported. This data does not say Aux is not on for some short periods at 13.5 degrees. It does say a 5 KWatt Aux element is on intermittently, not constantly when the temperature is 12 degrees, indeed the table shows a total of 5 hours at 2 degrees is expected and the Aux heat needed is 12 KWH, or just an average of 2.4 KWH per hour. That 5 hours is of course when I have the house set back to 65 degrees which makes the outside temps correspond to 7 degrees not 2 degrees, and the 7 degree data point shows 30 hours expected using a total of 69 KWH, getting real close to a 2 KW (6.8 KBTU) aux supplement needed. As I stated some somewhere in the past on this thread the Report shows the 3 Ton needs a total of 107 KWH Aux heat for the whole year.

Again, I have 21 years experience with a 4 Ton WF Geo HP and I have run it without the Aux connected. I have seen a lot of temps at 10 degrees when I got up in the morning and the HP was not running 100%, but it heat BTU output of my old unit is similar to that of the new 4 Ton proposed, and both have a balance point of zero degrees. And both assume a 8 KBTU "free heat" from sun, refrig, bodies, whatever and it seems that number isn't far off.

My house was built under "all electric" protocols in 1986 and has double insulation R38 or thereabouts. Of course when I run the insert I have to let some air in but the Insert is putting out more heat than the 4 Ton HP. I have no doubt about the 3 Ton (or 3..5 Ton - the label really applies to cooling on these units not heating).

 

[woodgeek]

Again, I am happy you have finalized your design and are ready to pull the trigger. As so often happens, where a person ends up is rather different from where they start out. I do that myself.

It seems that you started out being very satisfied with your previous 4 ton unit, comfortable, affordable, green. Does not need aux regularly, etc. That lasted for 20 years (and of course the loop is still aok).

Your first question to the board earlier in the year was whether if you downsized to 3 tons, would you use a lot of aux, b/c you wouldn't want that. You didn't have a lot of hard data to go on, but is sounded like yes, you would. Maybe a couple hundred bucks worth per year, not the end of the world, but there it was. You have a report full of numbers in front of you, that we can't see, and keep quoting numbers from it that do not appear to be mutually consistent. Most of the numbers you have quoted make it sound like your balance point on the 3 ton is going to be somewhere in the 20s, rather than somewhere in the single digits or low teens, like the old unit. Based on the BTU numbers you quoted, that is just the sort of difference in balance point one would expect from downsizing that much, and that we estimated earlier in the year.

But its cool, we still just think the smaller unit is going to cost a couple hundred dollars a year in extra aux. The only thing that has changed is how much you care about that much aux, now not very much. I think that is reasonable....maybe you were worried it would be really expensive, and when the pro projections come in a couple hundred dollars, it matters not.

Now you tell us that you are more worried about summer dehumidification, operating noise and avoiding start/stops (despite the previous 4 ton somehow being ok for 20 years), so you are going for the 3 or 3.5 ton. Ok. Done.

The second question was whether you should get another DSH. You said that you were never really satisfied with the one you got before, AND that you two needed very little hot water. We pointed out that for the same money you could get a v nice HPWH that will be more efficient, simpler and more compact (than two tanks) and work better than a 1 tank DSH system. Or for less money you could get a cheaper HPWH (that will likely last the 5 years you are in the house). Or for even less money, you could just run with the existing elec tank and no DSH, and the upcharge on your annual bill might be $100-150/year.

You heard all that, and then decided that you are getting a new DSH. I assume that some unknown reason came up that made the DSH more attractive. Ok, Got it. Done.

I DO like to argue, but we aren't arguing. You asked if a smaller geo would call more aux, and how much it would cost. The answer is yes, and the amount is prob a couple hundred bucks a year. You asked if there were better options than the DSH, that might be cheaper, more efficient, or both. Again the answer is yes, you could save $1k on install and get a more eff DHW system, or save $2k and have a system that costs $150 a year more.

You asked a couple questions to the board, got some answers, and then you and your pro installer discussed all the details and decided to get the smaller geo and DSH. Sounds like your installer did a good job of walking you through the decision process (something we can't do), allayed some initial concerns you had (as expressed here), gave you some various operating cost and install cost estimates that were acceptable to you, and you picked what you wanted.

 

[Jerry_NJ]

Thanks, suppose we've ran this on to the ground, or into the ground, geo : )

Side point, most of the responses I got earlier, not lately, on the same set of issues posted on the GeoExchange Forum, populated by more than a few "sellers", was I should consider going smaller than the 3/3.5 Ton. So I had that advice in my mind in all of our discussions.

Yes, I have proof that it is possible for a two stage compressor of the 1990s design (not a scroll) holds up well to what must be thousands of starts and stops. Right now it is heating and even some afternoons in the past week done some cooling and the compressor has a smooth humming sound which I hear only if in the basement... and an almost pleasant machine sound. That's one reason I went back to Water Furnace. As you come to know me, you may anticipate that my life with Water Furnace was not without complaint, but never against the installer or the general good performance and economics of the unit. My problems with WF came only after 15 years when I needed repair, my dealer had retired and I didn't pick the best replacement, and the poor job WF on parts supply, because my unit was so old. I understand they are an OEM and all of the rotating machinery they have thy buy on contract from a supplier/mfg who decides when to stop manufacturing an item, the case now even for the compressor in my existing unit. So, yes I like my existing unit and if I could replace the existing compressor (better if with a retro Scroll) for under $3K I'd do it. I have replaced the pumps and blower, the DSH pump is out but didn't plan to repair for the reasons you understand better than me, so a new compressor would have put my unit in the reliable column for another 10 years at least...yes there are connection and the condensor ... plus other relay stuff, plus electronic that are old. But absent a new compressor a complete replacement leaves a more comfortable feeling.

I post her seldom in recent times, but I came to The Hearth for wood heating exchanges and information and had no reason to visit here in the "Green Room" other than a few times as I don't consider wood heat "green" but do consider my Geo unit of 21 years to be an effort in the green direction and sound economically. I know I have saved at least $1,000 maybe $2,000 a year in the last five or more years over what it would have cost me to heat with oil. Yes, I've burned a couple of cords of wood, much paid for with sweat labor as I have over 5 acres - another green contribution I make. But before the Geo unit, when I had only an air-to-air unit I burned a couple of tons of anthracite coal in a coal stove in the basement. That looked clean, not much visible smoke, but we all now it was not and neither is my wood even though I installed a modern approved air tight insert in my fireplace a few years back - listed in my "signature".

As for the numbers I have in the study, I'm at least okay with numbers I have a masters in electrical engineering and about 40 years as an engineer and engineering manager. That helps me think logically, it doesn't make me a great typist (typos do plague my typing) or even necessarily as careful at with the content of my post/reply here, but I do nonetheless get usefull information, and some incorrect information. But even my medical doctors advice is subject to me making self-interest decisions on what I do next.

Thanks for working with me on this exploration on sizing a HP. On Hot Water generation, the decision is still very uncertain and if I go DSH i'll report my results here, results that will disclose numbers and methods of obtaining those numbers. But number absent any specifics on how much in electricity, rather how well the DSH heats water given my DSH/HWH management methods, e.g.,, use of timers and the like.

 

[woodgeek]

Something that I like about your process is that you are giving a thought to the next owner....

The next owner will either be like 95% of homeowners, and will happily pay the elec bill every month and never give a thought to the HVAC or DHW until it quits, or if a member of the other 5% (perhaps an engineer like us) and he/she wants to save money or energy, they will develop a plan to do so.

I think the most cost-effective way to save energy in your existing house would be a energy retrofit, which could likely drop your heating and cooling loads by 20-30%. A house of the 1986 vintage would be a prime candidate for such a retrofit these days....which would mostly be airsealing and ventilation work. After retrofit a 4T unit will be way oversized, and 3/3.5T will prob never need to call any aux.

I am NOT suggesting you undertake a retrofit project...IMO with cheap geo BTU and a 5 year horizon doesn't make sense.

So, from the next owners perspective, they either don't care (95%), or they will be happy with the 3T (5%).

 

[sesmith]

I'm a little late to this discussion, but I'll throw in my 2 cents, having lived with a climatemaster 3 ton system with DSH for the last 3 years and occasionally (rarely) using my wood stove.

You definitely want the DSH set up with it's own dedicated tank to be most efficient. FWIW, our DSH does almost all our water heating when our geo system is running steadily in the winter and almost none of our water heating in the summer. The average over the year works for us. A HP water heater may work best for you, especially if you could use the cool air it produces, and if its noise isn't an issue for you.

Ideally, to be most efficient, a geo system should be designed to use second stage, and even some aux heat during the winter. Even when aux heat is running, the system is still producing most of it's heat from second stage operation. It doesn't just switch to a COP=1. I measured my system's COP a couple of years ago at various times throughout the season. What I found was that in second stage, the system was basically as efficient as when it was in first stage (right around 4). When aux came on, it was still running with a COP of 1.87. AUX was only running for around 15 minutes of every hour as a supplement, so the system was still very efficient on an hourly basis. So I never worry when I see second stage on, and if I want to use my basically free aux from the wood pile (now getting very old in my yard), I'll fire up the wood stove on the nights it's below zero out.
One thing we experimented with, and do not do, is any setbacks, even though we like it cooler when we sleep. Our system just has to work too hard to bring the house temp back up in the dead of winter. There's just a lot of mass in my old house, and it seems to work better to keep the house at one temp. We opt to just close the heat ducts off in our bedroom and close the door when we're sleepi

You may want to post some of your questions to the geo forum as there are several knowledgeable installers that frequent it.

(broken link removed)

 

[Jerry_NJ]

Thanks, I have written the check paying 1/3rd of the contact cost and placed it in the envelope with the signed contract, didn't mail yet as the Government shuts down on Columbus day, nothing else does...go figure. I discovered it is Columbus day when I drove to the NJ auto inspection station and found it closed.

I have decided to go with the so called 4 ton unit, a close match to what I now have. The new 049 two speed Series 5 has a maximum (32 degree loop) Stage II heat of 37KBTU, my current is rated at 33 KBTU. I was told I can have the delay switching to Stage III heat (5 KW Aux) to be 30 minutes, which I plan to do. I also plan to have the fan manual operation to run at the Stage I level of about 1300 cfm to help move wood heat when the HP isn't running. My current manual fan speed is 1000 cfm. This is one way to cool the upstairs down, as the HP thermostat is in the living room and the wood insert will raise the temperature there above the 70 degree set temperature... the upstairs will drop to 65 or so even with the fan running to circulate air around the house.

Thanks for the good testimony on the DSH for hot water I have decided to include that unit and I plan to get by with a new 80 gallon AO Smith electric water heater with the lower element set at the lowest possible temperature, about 90 degrees I think it is. I also plan to simply shut the hot water heat off when the heat pump is running a lot, heating or cooling. The 4 ton DSH is rated at over 5KBTU input to the hot water when the water is cool (don't have the temperature, but suppose that sort of heat transfer occurs only when the tank being heated is closer to cold water temperature, say 55 degrees or so. I'll at least have a timer cut off to the hot water heating elements to shut down around 6 PM and not come back on before about 7 AM, or over half the 24 hour cycle. I believe these strategies will help the one tank system perform near that of a two tank system.

While I still like the idea of the smaller unit running a lot, even 100% with an outside temp in the lower teens, and using some Aux periods to supplement when the temp drops toward zero, that's unusually cold for NJ. A 10 degree morning was seen a few times last winter, but no zero readings.

I'm a 21 year veteran of Geothermal HP and know it has paid off even given the high initial cost, was about $12K including the ground loop back in 1993. The price has at least doubled in those 21 years, but the cost of heating oil as gone up over 300% in the same time while electricity has gone up less than 50% - I've saved at least a couple of thousand $$ a year in each of the last 6+ years. The cost benefit was about a wash with oil heat when I installed the existing system, and oil was under $1 a gallon, electricity about 10 Cents KWH. My electric provided provided about $3K incentive, making my cost about $9K in 1993.

But I still have to remind myself of how economical the HP is when running - my automatic reaction is to react negatively when I am aware (like when in the basement) the HP is running with concern about the cost. I had natural gas heat in the home before my current, and it then and now is very competitive and if I could have I'd have installed it here - I still like the 100KBTU heat with a register putting out hot not warm air. Yes, the warm air is more gentle and less drying. The house before last even had natural gas powered cooling - figure that one, guess it used gas heat to develop refrigerant high pressure, exhausting the heat into the outside air, and expanding the refrigerant to develop cooling...whatever it worked. That was Ohio and we saw one winter with a period of temperatures at 25 and more below zero, colder even than the temperatures I experienced in Denver Colorado. Boy that gas heat was nice, and ran a lot I'm sure - must have cost as much as $40 for heating and cooking that month. Well that was in the late 1970s, but even then $40 was affordable. I know some folks who had electric heat, and one who had an air-to-air heat pump. I think some of them saw $200 in electric bills. What was electricity then? maybe 4 cents a KWH. Sorry for the ramble, just remembering what affects my thinking and decision making.

I don't visit this forum often, but will come back after I gain this winter's experience to see if I can add any facts.

 

[woodgeek]

Or you could skip the desuperheater, use the existing conventional elec tank for your minimal DHW needs, and use the money you save to take the wife on a mediterranean cruise.

(broken image removed)