Trouble transfering heat to storage tank from Tarm

[free75degrees]

so are these the "integral ball valves" that are being referred to here?

...

Thanks for the tip free75... sounds like things got a little hot for you! I'm glad you had a happy ending so to speak. So by opening and closing those integral valves you think you freed something up and got it working better? I'm certainly wiling to give those a few twists back an forth. My tank is still at 155F today and the suns out so I may not fire again until we need some heat... but I'll give this a try and report back in the next couple of days after I fire it up again.

Yes those are what I am talking about and they all appear to be in the open position in your photo. As soon as I toggled those valves the boiler temp dropped rapidly after having been railed near 100*C. I think the termovar might have been stuck on all hot and toggling the valves got some cold to be included, so the heat was all of a sudden being dumped into the tank as it should have been doing all along. I am going to test it again tonight...

I know you have the bypass, but it still might be possible that your termovar is stuck on "all hot" and this is causing you problem. If it is stuck on all hot then the circ can basically pull from either the all hot termovar or the tank via the bypass. If the tank HX has more head loss than than the all hot temovar (which it probably does) then the bypass won't really be doing much - the termovar would supply almost all of the return water to the boiler due to the lower head loss.

 

[free75degrees]

I wish I had a termovar to take apart. I'd like to see what those "integral ball valves look like"

I was definitely upset when I broke my termovar flange nut and had to replace it with a black pipe fitting, but now I'm kind of happy it happenned because it allowed me to check out the ball valve on the flange I removed.

You actually can check it out if you really want to by closing all 3 valves then removing the termovar. You'd just have to be careful not to damage the bushings (maybe not worth the risk)

 

[Chris S.]

Stupid question here-what is the output of the boiler? I just checked Bioheat site and it seems to be around 198,000 btu/hr. I may have that wrong but I am thinking that if the Termovar is operating correctly, the boiler may be oversized for the output of the coil in the tank. It seems like the numbers look ok its just that the boiler isn't working hard to maintain those numbers. What are the coil specs?

Mike

Definitely not a stupid question. My Tarm lit also lists the 60 at 198,000 btu/hr. Our plumber/local plumbing supply house ran the numbers on our heating needs based on our building design then they collaborated with TarmUSA to size the boiler. I pushed for the 40 vs the 60 just to avoid the issues you raise, but the professional trades people seemed pretty confident we'd need the 60 so I gave in. There may not have been a good understanding of the storage tank HX limitations taken into consideration during that discussion. Little bit of a learning curve for everyone, unfortunately.

We have 3 STSS 180 foot coils, each rated for 39,600 BTUs. I don't know if you simply multiply by 3 and compare to the boiler BTUs, but if that is the case then perhaps our boiler is too big for the tank HX. Seems like there may be other factors involved, there must be loss along the way... I'm sure others on here are more qualified to answer this.

 

[Huskurdu]

Stupid question here-what is the output of the boiler? I just checked Bioheat site and it seems to be around 198,000 btu/hr. I may have that wrong but I am thinking that if the Termovar is operating correctly, the boiler may be oversized for the output of the coil in the tank. It seems like the numbers look ok its just that the boiler isn't working hard to maintain those numbers. What are the coil specs?

Mike

Definitely not a stupid question. My Tarm lit also lists the 60 at 198,000 btu/hr. Our plumber/local plumbing supply house ran the numbers on our heating needs based on our building design then they collaborated with TarmUSA to size the boiler. I pushed for the 40 vs the 60 just to avoid the issues you raise, but the professional trades people seemed pretty confident we'd need the 60 so I gave in. There may not have been a good understanding of the storage tank HX limitations taken into consideration during that discussion. Little bit of a learning curve for everyone, unfortunately.

We have 3 STSS 180 foot coils, each rated for 39,600 BTUs. I don't know if you simply multiply by 3 and compare to the boiler BTUs, but if that is the case then perhaps our boiler is too big for the tank HX. Seems like there may be other factors involved, there must be loss along the way... I'm sure others on here are more qualified to answer this.

I'm just a newbie to boilers...but you stated earlier that your delta T from your HX was about 20 degrees diff...which I've always heard was the real world goal....It sounds like your hx is working as designed....I maybe wrong here.

I also know next to nothing about Termovar valves, but considering the amount of copper in your system....it seems it might only take one little piece of solder roaming around you system to get stuck in your Termovar valve....just a thought.

 

[Chris S.]

I posted an earlier reply that got lost in the ether. Lots more activity on this thread since then. I'm going with the idea that the Termovar is either (a) not working properly, (b) not allowing a high enough flow rate, or (c) not allowing a high enough delta T.

A little more data would be good. You mentioned a 20 degree delta T across the tank HX towards the end of the burn. When the heat transfer was not going well, what were the three temperatures at the Termovar?

I'm assuming that the hot in (recirc) was 180, and the cold in (from the storage HX) was close to the tank temp - say 120 when the tank bottom temp was 110. What was the Termovar output (I assume that's also the Tarm input)?

Seems like it *should* be 140 under those conditions - just high enough to provide input protection. If it was 160 or more, the Termovar is being part of the problem.

A little bit of a rookie question here, am I able just to put a thermometer on exterior surface of the legs of the termovar to get these temps? I thought I read somewhere that the termovar was designed to return water at 160, is it 140? I may not fire for the next day or two, but when I do I'll try and collect this info. Good deductive strategy, thanks for the help!

 

[Chris S.]

considering the amount of copper in your system....it seems it might only take one little piece of solder roaming around you system to get stuck in your Termovar valve....just a thought.

very possible- I'm headed out to toggle the termovar's integral ball valves and see what I can shake loose, sticky valves, pieces of solder, etc.

thanks everyone for the help!

 

[steam man]

Stupid question here-what is the output of the boiler? I just checked Bioheat site and it seems to be around 198,000 btu/hr. I may have that wrong but I am thinking that if the Termovar is operating correctly, the boiler may be oversized for the output of the coil in the tank. It seems like the numbers look ok its just that the boiler isn't working hard to maintain those numbers. What are the coil specs?

Mike

Definitely not a stupid question. My Tarm lit also lists the 60 at 198,000 btu/hr. Our plumber/local plumbing supply house ran the numbers on our heating needs based on our building design then they collaborated with TarmUSA to size the boiler. I pushed for the 40 vs the 60 just to avoid the issues you raise, but the professional trades people seemed pretty confident we'd need the 60 so I gave in. There may not have been a good understanding of the storage tank HX limitations taken into consideration during that discussion. Little bit of a learning curve for everyone, unfortunately.

We have 3 STSS 180 foot coils, each rated for 39,600 BTUs. I don't know if you simply multiply by 3 and compare to the boiler BTUs, but if that is the case then perhaps our boiler is too big for the tank HX. Seems like there may be other factors involved, there must be loss along the way... I'm sure others on here are more qualified to answer this.

Thank you for not saying I am an idiot. LOL. Quite possibly the Termovar is not set up correctly, however, I just want to look at this other angle. If you took the output of the boiler of 198000 btu/hr at 80% efficient that comes out to 158400 btu/hr real output. 39600 x 3 = 118800 btu/hr heat load. Subtract that from 158400 and that leaves 40400 btu's with no where to go. Obviously Tarm may sized the heat exchangers correctly. I just wonder about all the assumptions that were made. Even if the termovar is operating correctly it seems as if your going to get some cycling unless you add some heat load. I have an issue with a solar system that is similiar to this situation. Anyone have any similiar experience with a gassifier cycling before storage gets up to temp?

Mike

 

[Nofossil]

Unless you have pressurized storage with PERFECT stratification, you are absolutely going to get cycling as you get close to max storage temp. The effective heat transfer capacity of any heat exchanger depends on the temperature difference.

If you can transfer 150,000 BTU/hr with a 40 degree temperature difference, you'll be nowhere near that when the temperature difference is only 10 degrees.

 

[Chris S.]

Unless you have pressurized storage with PERFECT stratification, you are absolutely going to get cycling as you get close to max storage temp. The effective heat transfer capacity of any heat exchanger depends on the temperature difference.

If you can transfer 150,000 BTU/hr with a 40 degree temperature difference, you'll be nowhere near that when the temperature difference is only 10 degrees.

The cycling occurred through out the process of bringing the tank up to temp- starting with the very first fire. Tank temp was 69F and within 45 minutes of start-up the cycling began. Through my education here on hearth.com I've come to appreciate the upper limits of heat transfer in the tank, and if cycling occurred only at 140F or 150F then I wouldn't be so concerned. Now that I'm finally up to temp, maybe my "problem" won't be so pronounced. I'll let the tank drift down to 110 or 120 and then see what happens when I fire it up again.

 

[Nofossil]

The cycling occurred through out the process of bringing the tank up to temp- starting with the very first fire. Tank temp was 69F and within 45 minutes of start-up the cycling began. Through my education here on hearth.com I've come to appreciate the upper limits of heat transfer in the tank, and if cycling occurred only at 140F or 150F then I wouldn't be so concerned. Now that I'm finally up to temp, maybe my "problem" won't be so pronounced. I'll let the tank drift down to 110 or 120 and then see what happens when I fire it up again.

Got that - I think there's still something wrong with the Termovar or system flow rates. Any chance of getting a full set of temps on your next burn, especially when storage is at its coolest. I'm thinking HX in and out, boiler in and out, and all three Termovar conections. Do you have an IR thermometer gun?

 

[EricV]

My Termovar did not come with those valves, maybe I got lucky. I did, of course , add my own.

I had trouble last year not getting heat through the termovar. This year I upgraded my pump from Taco 005 to tw0, 007's. the system works much, much better now.

 

[Chris S.]

Any chance of getting a full set of temps on your next burn, especially when storage is at its coolest. I'm thinking HX in and out, boiler in and out, and all three Termovar conections. Do you have an IR thermometer gun?

No, I don't have an IR thermometer gun... I'll ask around and see if I can find one to borrow. Any other way to get good temp readings?

 

[jebatty]

I have probe expresso milk frothing thermometers, 2" dials, 30-220 range, which I cable tied to various measurement locations and wrapped with insulation: boiler to hx in; hx to boiler out; tank to hx in; hx to tank out; boiler return; top of tank. They give a good relative indication of performance. I calibrated them all to the same base temp. Cost about $6 each on ebay.

Termovars are available with different preset temps, from 113 to 176. Mine, based on the probe thermometer, returns water at 130 minimum based on the balancing valve setting. If I opened the valve more, my guess is that return temp would go up, as I have limited quite a bit water flowing through the Termovar. The next time I fire the Tarm I will check that to see if the assumption is correct, as I think the actual Termovar preset is higher than 130.

Termovar info:
http://www.acaso.se/english/termovar_af.htm
spec sheet:
http://www.acaso.se/english/produktblad/TERMOVAR Ladd-ventil EN 0502.pdf

 

[chuck172]

I wonder if the people at Tarm even knew that the termovar had its own ball valves. They always recommended a balancing valve.

 

[MrEd]

So can I assume I don't need to purchase and install another balancing valve since my termovar already has them installed? That would be nice (especially considering I dropped $1500 on copper today!)

 

[chuck172]

No reason to add another ball valve there Ed, it might be more convenient though.

 

[Chris S.]

hello everyone- an update on my heat transfer situation.

We are just coming off of a warm sunny stretch here in Vermont and I haven't had cause to fire the boiler in over a week. I took advantage of this to let the tank cool down to almost 100F so I could do some work on sealing up the various holes to prevent evaporation and heat loss.

I also bought an IR thermometer gun so I could collect some information on the water temps going into/out of the Termovar, heat exchangers, etc.

So this morning at 10:30 I started a fire in the Tarm to start getting the tank back up to operating temp. As the fire got going I took some pliers and cycled the Termovar's built in ball valves/balancing valves several times to make sure they are open all the way, as free75degrees suggested.

I also closed the plumbed in balancing valve on the boiler input side of the Termovar a bit more, not all the way, but maybe 3/4 closed. I wanted to give that flow more resistance and hopefully get more pull on the loop coming through the heat exchangers in my storage tank, as some one here suggested that the resistance of all that copper coil in the hx might make it easier for the pump to pull hot boiler water through the Termovar b/c it is a much shorter loop.

I've been burning steadily since 10:30 and so far the fan has stayed on continuously- no cycling!

I'm still wary. Even with a big temp differential (theoretically easier to transfer heat) my system is barely keeping the water jacket below the cut off temps. I guess time will tell.

Currently the tank temp is about 128F. Water going into the tanks hx coils is 162F and coming out of coils at 130F.

The IR Thermometer gun I bought is a dud. I'm extremely frustrated as I really wanted to be able to watch the temps in/out of the Termovar- but the IR gun gives me dramatically different and unbelievable readings from copper pipes, brass valves and the steel/iron pump bodies. I guess you get what you pay for- my $50 IR gun from Amazon just doesn't cut it. I need to get some basic probe thermometers like jebatty suggested- should've done that in the first place.

I'll let you know how things go on the 2nd half of the tank.

 

[Nofossil]

Sorry - should have mentioned this earlier. You need to put masking tape or some other dull surface on copper pipe to use an IR thermometer. Copper is a perfect mirror at IR wavelengths so you get the temperature of some reflected surface, not the pipe itself.

 

[BrownianHeatingTech]

I wonder if the people at Tarm even knew that the termovar had its own ball valves. They always recommended a balancing valve.

You should not use a partially-closed ball valve that close to the Termovar, as it will create excess turbulence, and could cause a failure of the thermostatic element in the Termovar.

A separate ball valve is used in order to keep it (and its turbulence) further from the Termovar.

Joe

 

[Chris S.]

Sorry - should have mentioned this earlier. You need to put masking tape or some other dull surface on copper pipe to use an IR thermometer. Copper is a perfect mirror at IR wavelengths so you get the temperature of some reflected surface, not the pipe itself.

thank you- I'll give that a try and see if I get some better readings.

 

[barnartist]

For what it is worth, I also had a termovar-ball valves and all-must be the same model. I recal exactly the same problem now that I think about it. We could never get the storage tank up above 120 degrees. Eko 60-so the same size boiler. I remember how cold the return was going back to the boiler, and not being able to get the boiler to get going properly. If I recall correctly, the termovar's valves are open when you have them parallel with the water flow-there should not be any grey area or a slipping clutch-they are open or shut. The more I read your problem, the more I am finding similarities. Seems I remember taking out the valve(you can do this by shutting all of the termovars valves) and removing the inner auto valve completely to test the thing. use the manual valves to work the system for a fire cycle, and see what happens.
Bad news for us was this-this was my friends system, and he was so frustrated with it, he sold the sytem for a Central Boiler. I wonder now how much that termovar device played a roll!??
I want to see you get to the bottom of this, so I will be watching this post closely.

 

[free75degrees]

I just took my termovar apart to fix a leak on one of the ports. Before I took it apart I had made a total of about 5 fires and the first few had a similar symptom (Tarm kept cycling, the return water didn't seem to be cooling it down). When I took it apart there was a bunch of flat black plastic stuff partially clogging it. I think it was stuff from the inside of my black pipe. Could be a similar problem here.