Opinions Needed one my idea for a wood heat system.

[hkobus]

Or float some wax on the surface, I believe NoFossil does that, that way you can allow for some volume fluctuations without adding an excess of air to the system.

Henk.

 

[deerefanatic]

That's an awesome idea!

Might help with evaporation too....

 

[deerefanatic]

Ok, the local library can get me an interlibrary loan on "Pumping Away" so I can read that without buying it.... As well as several other hydronics books.

Now, some questions for you gurus!

Where I'd like to have my boiler, the piping lenghts will be as such:

To house: 100 ft

To Milkhouse: 55 ft

To Shop: 88 ft.

In addition, I'll have 14 ft of vertical piping (7 down, 7 up) on each run to get my lines below frost level. (Our ground heaves very badly and I don't want any chance of trouble down the road.)

Now, unfortunately, that's not the end of the story, the shop has a bit of a problem in that where my lines will come in is at the farthest point from where my radiant floor tubing comes up.... So I can pipe the water down one side of the shop, then across the other side (88 ft of run) or up the wall, across the ceiling, and down the other wall (65ft). Being in either case it will be inside the heated shop, I'll just use slip-on insulation for the pipes.

Now, my first question is: Can I get away with piping up and over the shop, or do I need to go around the perimeter with my piping? I was initially worried about exceeding the head capacity for my pump, but then got thinking that even though the water has to go up 12ft to get to the ceiling, it will then have 12ft of drop on the other side which should negate the 12 foot of rise once primed.... Am I correct in thinking this? If so, then running up and over should give the pump less "head" than around the perimeter by shortening the run by 20ft.

Second question: The calculated heat loss for my shop is about 55,000 btu/hr..... No, figuring that radiant slabs are efficient down to 80F water temps, I should be able to extract 700 btu's per gallon of supplied water from my boiler/hot water storage (conservative figure). Therefore a flow of 78.57 gph or 1.3 gpm will be necessary. That should be easily accomplished with a Taco 007 on 1" pex.. Right?

Third question: For the house, haven't calc'ed a heat loss analysis on the house yet, but I'm sure it's gonna be pretty high. So, planning on going with 1" pex again, but with forced air handler in the furnace. Probably need minimum water temps leaving the air handler of 100F right? if so, that be about 480 BTU/gal usable energy from my water (once again, conservative figure) meaning that 100,000 btu/hr (just a wild guess at the house's heat loss as of right now) I'd need 208 gph flow or 3.5 gpm. Once again, definitely seems possible with a 007 on 1" when the run will only be 100'.

Finally, the milkhouse will be heating DHW for milking..... We go through about 50 gallons 2x day..... about 84,000 btu/day in heat up + maintaining energy... I don't plan to have a flow-through setup to heat the hot water.. Rather, a large tank that can be heated by a small 10plate heat exchanger over a large part of the day, then can draw off the tank at milking time..... Since the water is used in large amounts, all at once, at two times a day that are roughly 12 hours apart.. I figure being it's only 55' from the proposed boiler location I should easily be safe with 3/4" pex for that..... Though if I'm going to have enough 1" pex left over from the other stuff, I'll sure as heck use it......

What do yall think? Correct me on any incorrect logic I've got here..... That's why I'm asking....

Oh, and yes; as soon as I get the time, I'm doing a heat loss on my house to have better numbers to work with.

 

[antknee2]

Once you understand the concept of primary secondary and all the features and benefits it brings to the table you will be convinced.

I have had other contractors come behind me and cut apart my systems and add ball valves between the tees. I sent Primary Secondary books to their company trying to explain the concept. They refuse to believe flow can move in more that one direction and at different flow rates in that piping. That concept has been around since the 60's. A B&G;engineer, Gil Carlson brought it to the industry back then.

Some old dogs refuse to learn new tricks

In the April 1999 issue of PMmag.com John Sigenthaler P.E. wrote an article "Mixing Wood with Water" It has some great info and formulas for piping and buffering wood boilers. I've done a few systems as shown in that article, including two of my own with excellent results. Siggy's own home has a 18" wide custom steel tank two stories tall about 20 feet long as a buffer tank/ radiant wall. Clever way and place to store that energy in the heated envelop.

I'd like to convince him to do a follow up control article. That seems harder than the piping to get right without some control wiring background.

I believe that article is still in the Archives at the PM site. It may not have all the pictures and diagrams however.

I've not seen a wiring specific article or book addressing wood boilers. NoFo is certainly capable of such an article It would be a huge help to the industry and wood boiler owners. I suspect there are a lot of swings and misses. I've had plenty myself when it comes to complex control logic and wiring.

Here are a couple reader friendly books on the primary secondary topic. Find them at www.heatinghelp.com bookstore.

hr

Think I found the article Anthony
(broken link removed to http://www.pmmag.com/copyright/ac719ac235fc7010VgnVCM100000f932a8c0____?view=print)

 

[deerefanatic]

I was thinking of doing a primary secondary setup with 1" lines going to the house and shop, then splitting there and having pumps for the DHW and air handler in the house; and pumps for the radiant and air handler in the shop.... Then I found this stuff on Pexsupply.com http://www.pexsupply.com/categories.asp?cID=1251&brandid;=

It'll be cheaper to run 2 runs of this stuff than to run 1 run of 1" and will allow me to move all my pumps, zone valves, etc into the boiler shed which would really be great...... Is that stuff good or should I be wary being it's so much cheaper than everything else I've found?

 

[Bob Rohr]

It's barrier pex with proper listings, it should be fine. Don't scrimp on insulation with all that exterion and underground piping. Buy enough r-value so most of your thermal energy gets to where you need it.

hr

 

[deerefanatic]

Yah, I'm getting an insulation contractor to blow urethane insulation into the trench.... R7 per inch, 4 inches all the way around for a total of r-28.... Sounds like enough to me I'd think? Or should I go more.......

He said I could do the 4" all around for about $4/ft, or 6" around (r-42) for $6.50/ft.... I'll have 240' of trench all total......

I've definitely decided to go with that Hydropex in 3/4 for another reason. I'd like to heat DHW year round, but also would like to supply cooled water to the furnace to work as A/C in the summer (run a HX loop through the creek to cool the water for the house air-handler....) With 1- 1" run that wouldn't be possible.... With 2- 3/4" runs it will work fine.

According to the Taco HVAC Solutions Software the head loss is only about 2 ft on the run to the house......

 

[deerefanatic]

Question for you guys on that HydroPex..... I called Pexsupply.com to ask if that cheap price was a limited time thing or normal... The lady on the phone matter-of-factly said that "No, that's the normal price. It's Pex-B which is a lower grade and therefore cheaper.."

Now, my question is: I thought the Pex-A, Pex-B, Pex-C nomenclature only referred to the process used during manufacturing..... Not necessarily quality..

Correct me if I'm wrong.....

I also looked at some Mr Pex pex-al-pex... About double the cost of the Hydropex, and not necessarily needed I'd think for buried lines...........

 

[deerefanatic]

Ok guys, here is a rough schematic. No valves or anything.

Thanks go out to the good folks at Taco for their free HVAC Solutions software...... Even though it can't really understand a true primary/secondary system (it wants the primary loop to go through the boiler... If you do it that way, it works fine.) and it doesn't show my buffer tank either.... (I'll plumb that the same as the boiler)

What think?

 

[deerefanatic]

Ok, now for some follow-up.... I've revised a few things shown in that drawing above:

First: According to the Slant/Fin Heatloss Express, the house has a calculated loss of 48,000 BTU/hr with 75F indoor temp and 10F outdoor temp. So I'm trying to size the system to deliver 125,000 btu/hr when the scorched air is running....... Or, about 13 gpm............

Second, the Shop Radiant heat slab is being calc'd at 75,000 BTU/hr, but the actual heatloss is about 58,000 at 65F indoor, 5F outdoor........

The small second air handler is just to heat my office (in corner of shop) the additional 7 degrees from 65 (radiant temp) to 72 (where I like to work on computers..

Now, I've been told not to try for a 20 degree drop in my radiant slab. So I've purchased a 3way thermostatic mixing valve (Heatgard 115H). To meet 75,000 BTU/hr with a 15F drop in water temp will require about 10.5 gpm..... Really more than 1" can handle in this situation.... so my thought is to pump hot (~180F) water straight out of the primary loop into the shop. Then have the thermostatic valve in the shop with the second pump to circulate through the slad. That way the 212' run of 1" pex only has to carry like 3 or 4 gpm of flow as it's just make-up water to keep the slad loop at around 110F....... Will this work or is it budget-enduced wishful thinking?

Here are some vital figures pertaining to my situation:

Loop Lenghts: From Primary to house is 140' of pipe, one way, for both the furnace handler and the DHW
From Primary to shop is 212' of pipe, one way, for both the slab and office air handler
From Primary to milkhouse DHW is 55' one way.

I plan to use the following size pipes:

House DHW: 140'+140' 3/4" Pex for total of 280'
Milkhouse DHW: 55'+55' 3/4 Pex for total of 110'
Shop Office Air Handler: 212'+212' 3/4" Pex for total of 424'
Shop Slab: 212'+212' 1" Pex for total of 424' to the Mixing valve, then ~ 6' more from mixing valve to radiant slab (with second pump thrown in there somewhere)
House Air Handler: 140'+140' 1" Pex + 140'+140' 3/4" Pex Manifolded together for total of 280' 1" Pex & 280' 3/4" Pex. This should be able to flow about 12 gpm while still staying under 6'/100 for pump head.

Will this work? I'd go with 1-1/4" to the house air handler, but it's soooo expensive and almost impossible to get fittings for (plus my crimp tool won't do over 1")

Just looking for advice before laying out the dough.

 

[deerefanatic]

Well, work is started!!

The excavator is here digging as I write this...... Then tomorrow the insulator comes to spray in the Corbond....

then I'll pour the slab and set the posts for my boiler shed, set the tank inside, and build the roof and walls around it.......

And at some point, finish the plumbing, electrical, and build the boiler........ Whew!

 

[Nofossil]

So... I'm probably missing something, but if your peak load is 48,000 btu/hr why design the system to deliver 125,000? It's good to design in a bit of margin, but that seems like a lot. It's driving up the cost of installing and operating the system.

 

[deerefanatic]

Yes, I know that..... But, I am simply very leery of the 48,000 btu/hr heatload........ Simple reason: when we quit using the indoor wood furnace, the propane furnace had to run almost continually on cold days just to keep the house at 65..... Now granted, its a hi-efficiency so it may have been modulating, I don't know..... But I wanted to be better safe than sorry....

so in a nutshell, that's why.... Plus, by running the extra pex now, I've got room for expansion (radiant, etc....)

the excavator got everything dug out.... He dropped the hoe into the ditch and had to have his son come over with the dozer and pull him out. (He was sitting astradle the ditch and it caved on one side...) but nobody was hurt thankfully...... Got all the pex run to the shop and milkhouse this afternoon, and got started figuring out a way to get the pex into the house....

Insulation guy comes tomorrow......... Yeehawww!

 

[deerefanatic]

The insulation guy came Friday.... $1600 later I have a nice thick layer of Corbond at the rate of 6.6R value per inch, 4 inches thick.... Plus about 1.5 inches of insulation between hot and cold lines.... Buried about 5 feet down.

I've got my conduit laid and the electric wire and control wires ran through it......

About 85% of the trench is now filled in as I write this (thank goodness for a neighbor with a skid steer!)