pressure storage flow piping

[powerspec]

I know of a system installed with two 500 gallon pressure storage tanks heated by an Eko 40. Of course the inlet and outlet piping is not exactly at the top and bottom of these tanks, just about a third of the way above and below center line. The Eko is stuggling to get the water heated up as most of the return water to the boiler is from the bottom most connection and so the loading valve keeps the boiler loop on bypass.
Does anyone out there have experience with storage like this piped so the hot water from the boiler is introduced into the bottom port of the storage tanks, forcing a more uniform temperature gradient and hopefully get the boiler off bypass sooner with wamer inlet water?

 

[Nofossil]

You want the EKO to struggle with cold water - that's the most efficient situation. More importantly, you want to maintain maximum possible stratification in your storage. That means flowing top-to-bottom when charging storage from the EKO, and bottom-to-top when withdrawing heat from storage.

Lots of threads on the benefits of stratification - do a search or just trust me on this one.

 

[jebatty]

...just trust me on this one

This is trust well-placed. Edit: If water from bottom of tank is 100F and Eko supply is 160F, you are moving 30,000 btu's for each gpm of flow. And water at top of tank is about 160F, great to draw from to supply system. If tank equally mixed, woud only have 130F to draw from to supply system, which may be indequate in many applications, plus would be moving only 15,000 btu's with each gpm, a 50% drop in btu transfer per gpm.

If water from tank is 160F and Eko supply is 180F, you are moving 10,000 btu's with each gpm of flow, a 66% drop in btu transfer per gpm. First example shows the efficiency.

 

[stee6043]

I know of a system installed with two 500 gallon pressure storage tanks heated by an Eko 40. Of course the inlet and outlet piping is not exactly at the top and bottom of these tanks, just about a third of the way above and below center line. The Eko is stuggling to get the water heated up as most of the return water to the boiler is from the bottom most connection and so the loading valve keeps the boiler loop on bypass.
Does anyone out there have experience with storage like this piped so the hot water from the boiler is introduced into the bottom port of the storage tanks, forcing a more uniform temperature gradient and hopefully get the boiler off bypass sooner with wamer inlet water?

In addition to what is mentioned above do you have a balancing valve (ball valve) installed on your bypass loop? Closing this down to roughly 1/8 open will help force some hot water into your system a little quicker. Most folks run with their bypass loops throttled way down, myself included...

 

[powerspec]

The stystem is not mine it belongs to a buddy. There is no throttle on the 140F Danfoss loading valve bypass loop right off the boiler. Why doesn't a throttle show up on any of the manufactures literature is the recommended piping layouts? If the Danfoss works right it shouldn't need a throttle valve. What are we missing here?

 

[Hydronics]

I have to run my 1 1/2" ball valve 1/8 open also. The Danfoss will protect the return temps. but it doesn't close off enough if there's substantial head in the loop. The literature that comes in the Danfoss box recommends installing a valve.

 

[jebatty]

Tarm manual shows a balancing valve too. If you haven't done it, put a thermometer (simple probe thermometer, meat or milk frothing, along the pipe and wrapped with insulation works well enough) on the return line after the Danfoss and before the boiler to monitor exactly what your return temp is. That will also tell you how much to close down the balancing valve. I think you want to set the valve to maintain between 140-160F on the return line once the boiler gets above 140. If your system return gets above 160, then your boiler return obviously will match. Once set, you can pretty much forget further adjustment to the valve unless you change your system in some way that results in too low or high temp.

 

[stee6043]

The stystem is not mine it belongs to a buddy. There is no throttle on the 140F Danfoss loading valve bypass loop right off the boiler. Why doesn't a throttle show up on any of the manufactures literature is the recommended piping layouts? If the Danfoss works right it shouldn't need a throttle valve. What are we missing here?

I'd have to do some digging but I'm 90% sure the sheet that came with my Danfoss valve shows the requirement for a balancing valve....

 

[powerspec]

Well you are correct the Danfoss lit and others do show a separate throttle. This seems to me an admission of design failure on the part of the loading valve manufacturers. If a throttle is needed to permit the boiler to warm up it is doing the job that the loading valve is supposed to do. Maybe this system should have had a 3/4 inch loading valve rather than a 1.25 inch size.
Do the systems using Laddomat or Termovar loading units also need throttles to permit fast startups of boilers with large storage volumes? My idea of how these controls should work is that they ought to take up a bypass flow postion just sufficient to maintain boiler infeed temp without any additional recirculation. The presence of a hand set throttle valve seems to prove that the loading units cannot work alone as intended.
On some of the Danfoss literature I recently checked Danfoss recommends a separate bypass line in parallel with the throttle bypass loop to force mixing of boiler outfeed water on systems with large storage capacity. The boiler circulator then is feeding two loops, one with the loading unit and another straight pipe in parallel with the loading unit. So an extra circulator is need to supply the loads. This seems to me a lot of extra complexity because the loading valve will not work alone.
I'm starting up a second Eko 40 system soon and I'd like to get it right the first time. As usual the comments on Hearth.com are much appreciated!

 

[DaveBP]

The loading unit type valves do have a balancing valve in addition to the thermostatic valve. It operates proportionally as the thermostat is shifting over to more and more return water allowed into the boiler. By the time the return water is hot enough it doesn't need any more supply water blended into it the balancing valve has completely closed off supply water from the boiler. More elegant but much more expensive than a regular thermostatic valve and ball valve combo.

I don't think a balancing valve on the simpler thermostatic valve is a failure of design. I think it is usually just dialed in to optimize the individual's system and then left there. Different systems can vary a lot in how water moves around. Lots of balancing valves in hydronic systems.

 

[dirttracker]

Unfortunately the loading valve will only fully close off the line coming into the valve from storage. The bypass loop does not have a feature in the valve to completely close off this port. The balancing valve is used to add some restriction to the bypass path promoting water flow through storage. I to think the termovar would work better if it could completely shut down the flow of water through the bypass port. I assume there was a reason it was not designed this way. There is an alternate I found by searching this site, but I have not tried it. There is an outfit called Fluid Power Energy (www.fpevalves.com) that makes a thermostatic valve that someone here had tried. it was posted on this site a year or 2 ago. I have thought about replacing my termovar with one of these, but the termovar works well enough that I don't feel like opening the system up to mess with it. However, I have thought that being able to completely shut off the bypass when the boiler return temp from storage is above 140 would provide a bit more efficiency. If anyone has first hand knowledge of any efficiency improvements from changing out a Danfoss or termovar loading valve for something that can positively shut off bypass loop flow, I hope they will speak up.

 

[DaveBP]

Here is some more info:

(broken link removed) Acaso/LK eng/Termovar_Laddpaket_ENG.pdf

(broken link removed)

The two terms for the different units, "loading valve" and "loading unit" cause a lot of confusion.

Edit: you'll need to cut and paste the 1st URL into your browser for it to work.

 

[dogwood]

I pulled up the above listed site for the Termovar Loading Unit, which I currently have in a box, and was reminded that the unit has an insulation cover that BioHeat, I believe, does not stock. I emailed the European company directly to see if there is any way to order it directly. It's a shot in the dark, but have anyone of you by chance obtained, or tried to, or might know how or where to obtain this cover? If my wife asks, I'm suggesting it as a perfect Xmas stocking stuffer.

I am going to insulate all my pipes, as well as the storage tank as most of you seem to, and am triyng to be as thorough as many Europeans in this regard. No sense in wasting perfectly good heat on a hot boiler room in the back of the garage.

Mike

 

[DaveBP]

I pulled up the above listed site for the Termovar Loading Unit, which I currently have in a box, and was reminded that the unit has an insulation cover that BioHeat, I believe, does not stock. I emailed the European company directly to see if there is any way to order it directly. It’s a shot in the dark but have anyone of you by chance obtained, or tried to, or might know how or where to obtain this cover? If my wife asks, I’m suggesting it as a perfect Xmas stocking stuffer.

I didn't ask Bioheat either. If you find a source for them, post it will you?

I'd be satisfied if that were all I got for Christmas. I have plenty of socks and gloves.

 

[dogwood]

Haven't heard anything back from the European company yet Dave. I'll keep you posted. Next time I call BioHeat I'll inquire of them as well. When I ordered the Termovar loading unit from BioHeat originally, they had on hand, and did include the add-on backflow prevention piece shown in the diagram your link led to. Maybe they can get hold of the insulation cover as well. Their salesperson also mentioned a Termovar Loading Unit with a bigger pump was in development and possibly available in the future.

For next Xmas, 2010, I would like an add-on Lambda unit for my Solo Innova, which is also currently unavailable, and probably way too costly if it was. As it is, socks and gloves are available at the mall.

Mike

 

[Gooserider]

If you can't get ahold of the factory cover at a reasonable price, I'd consider doing the home brew approach... I'd make a two piece cardboard mold around the valve and cover each half with a section of garbage bag, tape it up real good and then fill each side w/ "Great Stuff" or similar foam insulation (make sure it's rated for at least 200°F) - in essence a DIY version of the "Foam in Place" type packing machines you sometimes get stuff in...

Probably wouldn't look as nice, but figuring the only real material cost is a can of spray foam, and some duct tape, might be a heck of a lot cheaper...

Gooserider

 

[dogwood]

Sounds like a good Plan B Gooserider. I emailed the company in Sweden listed on the brochure again at [email protected] to see if they would even acknowledge getting the first email. Their website is (broken link removed) if anyone else wants to give it a try. Maybe I should to appeal to Hanson for help. Bet you he could get through to them.

Mike

 

[Hansson]

I have mail them about the insulation

 

[jebatty]

From recent experiments, I found that my Tarm burns much hotter, therefore supplying more btu's and operating closer to its capacity if 1) I let the boiler come up to about 185F before I start the circulator and 2) I make sure the balancing valve for return water protection is tuned to insure 140-160F return water protection. Before doing this, with 120F system return water, boiler output would be 160-170F until system return temp started to rise. After doing this, boiler output was in the 183-190F range. See this thread.

 

[dogwood]

Thank you so much Hansson. Hope you have better luck than I have. So far neither the European company or their American distributors have responded to my emails asking how I might obtain that Termovar insulation cover.

Mike

 

[Hansson]

Thank you so much Hansson. Hope you have better luck than I have. So far neither the European company or their American distributors have responded to my emails asking how I might obtain that Termovar insulation cover.

Mike

Got the answer today.
Hi,

Unfortunately, it can not be ordered in the United States. But it is the same insulation that we use in Sweden.


Sincerely / With best regards / Mit freundlichen Grüßen
Magnus Granehed

I can check the price in Sweden.Maybe i can send the to the US?

EDIT:The price is 130 SEK I wonder how much the fraigt cost is?

 

[dogwood]

Hanson, Thank you so much for finding out that information. It is very kind of you to offer to obtain and ship one, but I would not put you to that much trouble. I will pester BioHeatUSA to see if they will get one for me. By the way 130 SEK (Swedish krona) comes to only $18.10 (American) which is quite reasonable. Tack så mycket.


Mike

 

[rickh1001]

I have a quick question about the discussion of the Danfoss valve. I have a balancing valve on the short recirculating loop through the Danfoss, while the bottom of the storage tank feeds into the other leg - a more or less standard setup. The storage is within 10 ft of the boiler with 1 1/4 plumbing, so there is very little head loss through the entire boiler/storage circuit.

What happens if, once in operation and running at temp, I close off the bypass valve completely, and force all circulation through the storage tank? In a cold situation, this would be bad, since no boiler hot water could circulate past the sensing element on the Danfoss, and thus no water at all would circulate in the system. Once up to temp though, I would like to force most of the flow through storage, rather than just recirculate it around through the boiler.

So I guess my question is, is there any flow at all through the Danfoss from the cold inlet side when it is fully closed at say, 120F?

BTW, when I am running well and everything is at temp, the bottom of storage feeding into the Danfoss is typically around 150-155F, with the top of the storage at 175-180, and the boiler running at close to 190F. So I wonder whether I am still getting too much water through the bypass loop, rather than having it run through and fully charge the storage. I typically have the bypass valve cracked open only about 1/8th, but even that seems to be letting too much water through the bypass circuit.

 

[jebatty]

Not exactly what you want, as I have the Termovar, but may be useful. The Termovar always allows some bypass flow; perhaps the Danfoss does also. If system return is 150F+ so you don't need return water protection, my guess is that if you shut-off the bypass completely, thus forcing all return water through the system return side of the Danfoss and to boiler return, you likely will achieve higher system gpm but possibly somewhat restricted if the Danfoss does not open completely in its fully open state.

I have shut off the bypass completely on the Termovar when system return is 150F+, and system gpm increases. The risk is that you may forget to open it again in a situation when you need return water protection. I think the safest thing to do, unless you always have system return 150F+, is to have a temp sensor on the boiler return line after the Danfoss to monitor boiler return temp, and then set the bypass at a minimum point to provide the level of protection with which you are comfortable (maybe 140F minimum?).

 

[rickh1001]

jebatty,

Thanks. It probably is important to leave some bypass flow, and not to shut the bypass valve completely, if only because I could forget to open it when cold. I am not sure if the Danfoss passes any flow from the cold side when it is completely closed. I suppose an ideal valve would close the bypass as it opens the inlet - a job that the manual bypass valve does with my Danfoss setup. I guess that is what the Tamovar valve does, although I don't know why there is a need for any bypass water once the system is up to temp.

The other thing I need to do is check the temperature gauges. These things are not highly accurate, and it is possible that I am getting higher charging temps out the bottom of storage than I think, as that one thermometer is a magnetic stick-on type. None of these are exactly NIST traceable high quality items!