Getting the most from Big BTU's Termovar , Danfoss , Loading unit ?

[webie]

I keep thinking I could get more from my system ? My current setup is a Tarm solo 60 and a hybrid storage system of 370 gal. pressurized storage and 1200 gal. unpressurized storage. How it is set up system charges and return temp control by a termovar and a B & G NRF 36 pump = ( grundfos 26-99 ) .
My return comes both from my storage and from my 5 zones to a Tee shortly before the termovar and since I use radiant in floor in 1 zone my return temps before the termovar can be anywhere from 100 to 160 + degrees .
I am trying to keep the solo 60 in the burn more rather than idling but with the big swings in return temp the only way I can do that is by camping out with my balancing valve trying to hold my return temps . The termovar seems to be rather loose in its ability to contol return temps .
I have been told that a loading unit wont help me out because I need a bigger pump then they have because of me charging my unpressurized storage with 3 - 180ft 3/4 copper coils and I need to have at least a 20 gpm pump to handle the solo 60's output .
Just wondering if there are any guys out there that have had better luck with a Danfoss VTC valve or have I been told wrong about loading units not being able to handle 200,000 BTU output with the coils in my storage ?
I typically can use supply temps from storage all the way down to about 135 so my storage be all the way down to about 120 on the bottom of my tank before I recharge . I can have zone returns anywhere from 100 to 160 if they call for heat ,priority goes to zone by weighted gate valves but I still get some flow from storage return when I am burning .
My feeling is that my termovar is just a restrictive T in my pipe.
Your thoughts Guys ?

 

[Bob Rohr]

I keep thinking I could get more from my system ? My current setup is a Tarm solo 60 and a hybrid storage system of 370 gal. pressurized storage and 1200 gal. unpressurized storage. How it is set up system charges and return temp control by a termovar and a B & G NRF 36 pump = ( grundfos 26-99 ) .
My return comes both from my storage and from my 5 zones to a Tee shortly before the termovar and since I use radiant in floor in 1 zone my return temps before the termovar can be anywhere from 100 to 160 + degrees .
I am trying to keep the solo 60 in the burn more rather than idling but with the big swings in return temp the only way I can do that is by camping out with my balancing valve trying to hold my return temps . The termovar seems to be rather loose in its ability to contol return temps .
I have been told that a loading unit wont help me out because I need a bigger pump then they have because of me charging my unpressurized storage with 3 - 180ft 3/4 copper coils and I need to have at least a 20 gpm pump to handle the solo 60's output .
Just wondering if there are any guys out there that have had better luck with a Danfoss VTC valve or have I been told wrong about loading units not being able to handle 200,000 BTU output with the coils in my storage ?
I typically can use supply temps from storage all the way down to about 135 so my storage be all the way down to about 120 on the bottom of my tank before I recharge . I can have zone returns anywhere from 100 to 160 if they call for heat ,priority goes to zone by weighted gate valves but I still get some flow from storage return when I am burning .
My feeling is that my termovar is just a restrictive T in my pipe.
Your thoughts Guys ?

Sounds like the HX cannot move the energy that the boiler is giving you, as the tanks warm up? There is some limitation to a coil HX is a tank of still water. Heat transfer drops as the delta T between the tank and the coil tighten. This is why those last 10 degrees or so are slower to push into storage compared to heat transfer when the tank is cold. You might not get the tanks to the boiler temperature.

BTU formula rate of heat transfer= 500 x flow (∆T)

Plug your observed numbers into the formula to see what goes on. Maybe use 20 gpm for the flow for that 200,000 input

With an external plate style HX you can get tight "approach" temperatures, down to 5° when sized correctly. The main difference is you have two "pumped" flows and this drives the heat transfer more efficiently.

A thermostatic type of mixing valve does take time to respond, it's not like a motorized valve that responds almost instantly. Sometimes folks try to force them into an operating condition with balancing valves and don't allow them time to react and regulate on their own.

 

[webie]

Observation right now since I started the boiler , bottom of the tank was at 114 The main pump kicked on at it set 165 boiler return was at 142 . Boiler ran about 10 minutes or so boiler supply was at 160 boiler return was at 138 tank return 116 . About 30 minutes into the burn boiler temp runs up continually till boiler kicks out at about 190 , return mix now at 162 tank return is at 116 . Boiler then idles till it drops back to 170 and return mix is about 144 I think this termovar is a high priced Tee and my balancing valve does all the work . My wondering is if there is a better way to control and stabilize the return temp to a more constant 140 or so degrees my boiler would stay in the burn cycle and it does pretty good as long as I camp out by my balancing valve .
Is there a better way or is the best we get with my set up . According to what I know about the termovar is the water from the supply side of the boiler is wide open all the time and the only way to reduce it is by the balancing valve , This seems kind of a crude way to control return temps although it may work for some it doesnt seem to be tight enough to handle my arrangement . What I have read about the Danfoss VTC is that it actually shuts off the boiler supply side if the return water is hot enough if thats true which I dont know ? Or does a loading unit have enough GPM to handle the out put ?

 

[maple1]

FWIW - my LK810 loading unit that has a 15-58 pump built into it handles pumping heat out of my 40kw boiler on low speed just fine.

 

[webie]

Thanks for your input Maple1 . I see in your set up how that work . I was told by one guy that a LK810 doesnt have enough capacity for 60kw boiler heating unpressurized storage through my HX setup . Has anyone tried it I sure hate to throw 700 bucks at something that isnt going to do the job.
Or is anyone useing a Danfoss VTC with better luck ?

 

[kopeck]

I'm somewhat in the same boat.

I have a Tarm Solo Innova 30 and while I'm getting good transfer with my exchanger (the water coming back from the tank is always with in a couple of degrees of the tank temp) it's just not moving the water fast enough at times.

Pretty much as the tank and boiler temps start to get closer, in my case around 160 degree the Temovar's pump isn't pumping fast enough to keep the boiler from idling. In my case it's not a huge deal most of the heating season, it only happens a couple of times per burn and the idle time is short. I would love the thing to charge the tank with out idling right up to it's top temp but the idle time is short enough that I haven't seen any adverse effects (creosote buildup etc). On a good cold day it's not an issue at all as the house eats up enough heat that it never idles. I also get around idling a bit on warm days by using small fires to heat the tank verse one big one. It's an inconvenience but I feel it's better for the boiler.

I've thought about how to fix the problem but I'm unsure what the best way is. I'm not sure if you can stuff a bigger pump into the Temovar's housing, I'm guessing not. A helper pump is an option but I wonder how much it would interfere how the Temovar operates (ie on startup when it's closed the helper pump would be dead heading).

I would have to think with a 60kw boiler things would be much worse but then again I don't know how much head your exchanger is giving you.

K

 

[maple1]

This sounds like a situation that would benefit greatly from some added VS control capability - say that NoFossils Vesta (not sure I got that right) setup allows. As supply temps rise, the loading circ speeds up, then as the fire dies out, it ramps back down. My stays on low all the time , but admittedly it would likely also benefit from such a setup since when my storage return gets above the magic 140 point, both boiler supply & return then start rising together with the supply rising more. By the time storage is getting close to charged, the boiler supply is a bit hotter than I'd like to see - in the 195 range. Not an issue for me the way I'm running things this year & not pumping my storage hot as I could - but it would likely lessen the heat that was making it to my chimney a little bit.

 

[Fred61]

I'm somewhat in the same boat.

I have a Tarm Solo Innova 30 and while I'm getting good transfer with my exchanger (the water coming back from the tank is always with in a couple of degrees of the tank temp) it's just not moving the water fast enough at times.

Pretty much as the tank and boiler temps start to get closer, in my case around 160 degree the Temovar's pump isn't pumping fast enough to keep the boiler from idling. In my case it's not a huge deal most of the heating season, it only happens a couple of times per burn and the idle time is short. I would love the thing to charge the tank with out idling right up to it's top temp but the idle time is short enough that I haven't seen any adverse effects (creosote buildup etc). On a good cold day it's not an issue at all as the house eats up enough heat that it never idles. I also get around idling a bit on warm days by using small fires to heat the tank verse one big one. It's an inconvenience but I feel it's better for the boiler.

I've thought about how to fix the problem but I'm unsure what the best way is. I'm not sure if you can stuff a bigger pump into the Temovar's housing, I'm guessing not. A helper pump is an option but I wonder how much it would interfere how the Temovar operates (ie on startup when it's closed the helper pump would be dead heading).
problem
I would have to think with a 60kw boiler things would be much worse but then again I don't know how much head your exchanger is giving you.

K

I have a 500 gallon stainless chemical tank for my unpressurized storage and have more or less conquered the problem but not completely. I'm heating the tank with a flat plate and the coil within only supplies the heating load. I set up an "overheat" zone that consists of an aquastat in the spare well on the boiler which operates a second circulator that pumps boiler water through a second smaller coil lying in the bottom of the storage tank. I have it set for 180 so when the boiler starts approaching the upper limit the overheat circulator kicks on and helps the main circulator. It may screw up the stratification but at that point in the burn the water is pretty much mixed.

 

[kopeck]

I have a 500 gallon stainless chemical tank for my unpressurized storage and have more or less conquered the problem but not completely. I'm heating the tank with a flat plate and the coil within only supplies the heating load. I set up an "overheat" zone that consists of an aquastat in the spare well on the boiler which operates a second circulator that pumps boiler water through a second smaller coil lying in the bottom of the storage tank. I have it set for 180 so when the boiler starts approaching the upper limit the overheat circulator kicks on and helps the main circulator. It may screw up the stratification but at that point in the burn the water is pretty much mixed.

That's a really clever idea!

I'm going to have to think that one over. Adding another coil, a smaller one and an extra circulator wouldn't be all that hard. I have an extra Taco 007-f5 as it is, it would be overkill probably but I have it on hand. An extra coil wouldn't be cheap BUT it wouldn't have to be huge either.

I'm going to have to look and see if I have an extra well on my boiler now.

K

 

[Fred61]

Just add it as if you are adding another zone with weighted check, etc. I'm controlling mine with an aquastat I had laying around that makes on rise but I would like to eventually install something like a Johnson Controls A 419 so I can monitor and easily change the temperature and differential.

I had this circuit plugged into my switching inverter up until I installed my standby generator but I'm thinking about plugging it back in since my generator failed to start on this week's exercise run.

 

[kopeck]

Just add it as if you are adding another zone with weighted check, etc. I'm controlling mine with an aquastat I had laying around that makes on rise but I would like to eventually install something like a Johnson Controls A 419 so I can monitor and easily change the temperature and differential.

I had this circuit plugged into my switching inverter up until I installed my standby generator but I'm thinking about plugging it back in since my generator failed to start on this week's exercise run.

Oh sure, I understand the concept, pretty simple really that's what makes it great!

Thinking out side the box here...

Since my coil exchanger seems to be up to the task it's the pump that's not pulling it's weight what if I piped it up just like you did but instead of the second exchanger just Tee into the current one.

Maybe someone with a better understanding of these things could chime in? I guess the "gotcha" would be if done incorrectly it could short circuit the whole thing an skip the exchanger entirely.

The power outage bit would also work well!

Thanks,

K

 

[Fred61]

Perhaps it's possible but you're exceeding the limits of my knowledge. Don't know much about flow capacities and heat transfer. The beauty of the coil laying on the bottom is that, in theory, it's in the coolest part of the tank. Best place to be if you want to use it for emergency cooling.

I don't know if a short circuit would occur or not. Would the circuit with the shortest run take priority?

 

[Fred61]

You could reach the limits of the coil to transfer the heat to the higher temperature storage water and just be pumping your heat around and around back through the boiler and accomplish nothing. It certainly would be a lot more efficient to have it's own separate coil. This thought was keeping me awake. Now back to sleep in my recliner.

 

[Armaton]

I always thought the slower the water in the line, the more heat that would transfer, therefore cooler water back to the boiler and less idling. Am I in error? It also might even out the temps for your Termovar, can only think that with several differing temps coming back to it, at different times,and it not meant to be instantaneous, that you might have trouble with it. Also is it possible for you to cover some of your nozzle/s, as some others have done with they're 60KW units? If you have 1 1/4" or 1 1/2" for your boiler loop, would think you could get away with much less pump. Just my thoughts.

 

[RobC]

I haven't been around for awhile but I have a Tarm 60 and had similar problems. I had to upgrade my circulator to a grundfos 26-99 and run it on low speed with the standard Termovar. This ultimately solved my problem. If I run it on Medium or Hi it will idle. Armatron's comment is correct but there are other factors to consider too.
To get to this point I had an accurate head loss calculation done and pump recommended. It was noted that I might want to run on low... Who would have thought ?
Before you change anything I would recommend getting an inexpensive inferred thermometer (http://www.amazon.com/Thermometer-AR550-Mini-Infrared/dp/B000MX5Y9C) for example. Spray paint areas you want to meter with some flat black paint so you get consistent readings. By doing this at mixing valves and heat exchangers, supply & return lines and Tee's etc you will get an idea of what is really going on.
My system charges in two stages so to speak. All storage water will pass thru boiler 2 times. First pass the Termovar will bring cold storage water (130's - 140's) up-to 160's in mixing mode. Second pass the Termovar opens and 160 water will go to 180+. However at no point does the boiler idle.
Most of my water goes to and from storage. Take a close look at where your returns dump into tremovar. Could that 100 degree return water be keeping the Tremovar closed too much of the time. Do you have " Ghost Flow " causing problems ? Maybe the 100d return needs to be relocated to get mixed with other return water farther away from the Termovar ?
Other mixing valves do work differently but that really might not be a problem. I looked into that option. All thermostatic valves take time to react to temp changes.

 

[kopeck]

I had to upgrade my circulator to a grundfos 26-99 and run it on low speed with the standard Termovar. This ultimately solved my problem. If I run it on Medium or Hi it will idle.

So you were able to use that pump in the Temovar's housing?

Interesting. I had assumed that the housings were sized to the pump/impeller.

I also find it interesting that you will get idling on the two higher settings and not the low one. I'm wondering if that's due to your pressurized storage getting mixed and hotter water returning? With exchangers, at least in my case, head seems to be the issue and more GPM would be better.

K

 

[webie]

Hmm I might be getting confused here which seems to happen the older I get but are we talking about just the termovar tempering valve or the termovar LK 810 loading unit ?
Maybe what we should all talk is either termovar as in Termovar tempering valve , loading unit as in termovar LK810 loading unit or danfoss as in danfoss VTC valve .
I have dwell thermometers for monitering the temps so its not necessary for me to use my IR gun which I also have . I have tried all three speeds on my pump and the lower the speed the more cycling I incure .
I like the idea of the flat plate heat exchanger to heat the unpressurized storage reducing my head pressure but after thinking about that I think I am kinda SOL because of how I am set up now . I could put in the heat exchanger but then I would have to plump in a expansion tank , pump and water source to my coils as they would be a seperate heating source . I think under that thought I would be better off to just use the water in the unpressurized storage and pump from storage tank thru flat plate heat exchanger back to top of tank . Either way it would involve a big project to fix my design problem .
I am still pointing my finger at the termovar being wide open on the supply side giving me the cycling . What I have been watching is my delta T between return and supply and if I can stay 30 degrees or more I can stay in the burn .

It seems that if I adjust the balancing valve so i am 140 to 145 I can stay in the burn but if my storage and zone returns warm up 10 degrees from when I set the balancing valve so does the return to my boiler and I will cycle to idle .
What bothers me the most about this is if I set that balancing valve when supply is say 170 - 175 and I do heat up and cycle . the next time before it comes out of idle I will see temps down in the middle 130's and I certainly dont want to be distroying the boiler .

 

[webie]

So you were able to use that pump in the Temovar's housing?

Interesting. I had assumed that the housings were sized to the pump/impeller.

I also find it interesting that you will get idling on the two higher settings and not the low one. I'm wondering if that's due to your pressurized storage getting mixed and hotter water returning? With exchangers, at least in my case, head seems to be the issue and more GPM would be better.

K

I too thought the only pump that fit in the loading unit was the smaller grundfos . It sure would be nice with a 26-99 and being able to hold return temps at 140 till my storage gets up that high .

 

[webie]

Is anyone useing a Danfoss VTC with a 60kw boiler and how well does it work ? What I have read is it acts more like how a loading unit operates and less dependant on operator interaction with a blancing valve ?

 

[700renegade]

I have a new Danfoss VTC on my Vigas 80. My 'balancing' valve is there just as an isolation in case I need to service something. It's been wide open since the day I installed it.

near as I can tell the VTC is 100% recirc only till 140*, it blends to about 160* and after the return water hits 160* it's fully opened to the return side only. I know until 140* my hot manifold with a Grunfos alpha pulling on it 20' away stays cold. I can tell by the GPM reading on the Alpha about how far open the VTC is. GPM raises fairly linear between 140 and 160*. I see no need for a balancing valve in my setup.

 

[RobC]

Just to clarify I was referring to Termovar loading (mixing / loading) valve only... not pump & valve unit.
I bought my Solo with the near boiler plumbing already done. I don't have a balancing valve ( ball valve ). I use the shutoff that is part of the Termovar. I have the tempering water, (boiler side) of valve barely turned creating a restriction. It certainly not at 45 degrees. For the most part it is wide open. You might want to try wide open and see what happens ? In this position my water going into boiler is 137 degrees at start up. Not what the book says but 1) there's a wicked hot fire going on in boiler so I doubt it about condensation. 2) It's a constant temp returning so there is no shock going on and 3) It works for me. There are many give and takes with these setups like the positioning of the air vents for example.... ( Jeez... I didn't just bring that up ) I mean there is good better and best.... Sometimes we have to go with it works....
I have my boiler set to run at the hottest temp you can turn it up to. If I go to a lower boiler set point mine with cycle in-to and out-of idle.
In fact when it gets wicked cold outside, 10 and below. I run my boiler at a lower temp and let it cycle. Storage acts more like buffer tanks. I'm around a-Iot during the winter, this way I don't have to start 2 fires a day fires.
My setup is to primarily charge storage. I have a combination of 1.25" and 1.5" supply and return piping. When I get to the storage tanks it goes to 2". Slowing the water down even more and inside the tanks on the end of the dip tube I have a baffle so the water doesn't mix. My tanks are 2 stacked 500 propane with 2 X 6" ID pipes welded between them again to reduce mixing and to keep overall height to a minimum.
Regards Rob

 

[webie]

Thanks guys for the reply's . RobC I too was wondering if I might just turn up the boiler temp just to keep it in the burn cycle , but with my tank liner I am a bit worried of overheating it . Pump size head pressure and volume seem to be the only cure all to keeping the solo 60 from cycleing useing a termovar and with my heat exchangers being 3 - 180 ft runs of 3/4 inch copper coils my flow resistance is high . I know the solo 60 produces alot of BTU's But my goal is to try grab all of them and either store them or use in my zones as needed with out idleing from the get go . I can see where it works with pressurized storage or a different type of heat exchanger for heating the unpressurized storage say a flat plate heat exchanger as there is much less flow restrictions .

 

[webie]

I have a new Danfoss VTC on my Vigas 80. My 'balancing' valve is there just as an isolation in case I need to service something. It's been wide open since the day I installed it.

near as I can tell the VTC is 100% recirc only till 140*, it blends to about 160* and after the return water hits 160* it's fully opened to the return side only. I know until 140* my hot manifold with a Grunfos alpha pulling on it 20' away stays cold. I can tell by the GPM reading on the Alpha about how far open the VTC is. GPM raises fairly linear between 140 and 160*. I see no need for a balancing valve in my setup.

700renegade I am most interested in the danfoss VTC valve you are using and think this is probably the answer to help me keep from idling as much as I do . I researched the valve bit and it sounds like it operates more like a loading unit does shutting off the supply completely once the return temp has reached 140 +18 = 158 degrees if I get that right . I need to get rid of my balancing valve its to much of a PITA .
If you could give me more on the stats on what you see as your boiler heats up your storage as in what kind of temps you see from your boiler supply and your returns before the danfoss VTC and then what you see coming from the Danfoss . I am kinda curious as to what I could kinda expect .
Just wondering where you might live we may not be that far apart I am just south of GB about 45 miles ?
Are there any other guys running the danfoss VTC I would be interested in knowing how its working for you and what kind of temp stats you have ?

 

[RobC]

Wasn't thinking about a liner. There are some high temp liners but that's a project and expense.
But, the boiler water is going to some sort of exchanger so it's not like you actually heating the liner up to the boiler temp. You do have a high tank temp shut down ?
You mention you idle at 190 mine set all the way up idles around 200....
I keep thinking about the different return temps right at loading valve. If you were doing some re-piping could you put in a return buffer tank to help equalize the return temp so your not all of a sudden dumping in 100d water ? I don't see how any thermostatic valve is going to like that....
Rob

 

[webie]

Rob The water does mix a little before the termovar as we are talking a 3/4 zone return from my radiant miuxing into 1 1/4 return from my storage . It slowly falls to that temp because of priority with my weighted gate valves , at least thats what I see . I already have buffered it because it was a 3 way tempering valve and the return was the dump from the cool water from my radiant . But when the water from the radiant is 60 degrees or cooler because the temp is only set at 45 it takes a lot already to bump that up to 100 .
I just ordered new guts for the termovar . I am going to rule out that the element is no good by rebuilding it . If that doesnt change things the termovar is going to be an ebay item .
I figure thats the easiest thing to do before we start changing plumbing or ?
Would be nice if there are any other guys running a danfoss VTC with storage and how its working for you ?