Heating Storage Tanks

[markburtenshaw]

Hello all, I am a newbie to the wood boiler world and have a few questions!

Installed system is an EBW-300 with 2000 gallons of storage (2 separate 1000 gallon tanks plumbed in parallel).

Will have to forgive my ignorance as I'm a lowly controls guy so I was good with the electrical side of things including some custom software to help monitor and control things, but not so much on the mechanical side.

I had the system installed to heat the tanks with either a mixing valve or a bypass to control heating with direct injection methods.

I've had the system up and running for a few weeks now and so far am impressed with the EBW it is very solid, but I still need some lessons on heating the tanks properly. I am hoping someone can give me some insight on effectively and efficiently heating my storage tanks. the Mixing valve has a thermostat set for 150 deg F, but after speaking with the manufacturer that means it will not open up until 150 deg water is coming from my tanks?? That is why I am now primarily using my direct injection method and am able to keep the boiler loaded down with water temperature ranging from 175 to 185, but as I mentioned earlier I have 2000 gallons of storage so this will take days to raise the temperature?

The timing of my start up wasn't ideal, my initial tank temperatures were about 55 deg F so while my boiler has a lot of capacity from a BTU stand point I've only managed to raise the tanks to maximum of 120 deg F which still lasts about 2 days with my new house construction, but my goal was to raise the temperature of the tanks to 180 to 190.

Any thoughts?

Thanks!

 

[DaveBP]

schematic?

 

[markburtenshaw]

schematic?

If your talking about the mixing valve here is a link to the spec sheet:
(broken link removed to http://www.fpevalves.com/files/specsThermostatic%5C2010.pdf)

I have it hooked up in the mixing valve configuration.

I have also attached the mechanical schematics I drew up for the plumbers.

 

[Chris Hoskin]

with a Termovar-type mixing valve at your boiler it will take a LONG time to get those tanks up to temperature for the first time. I would expect that once you see return temperatures above 100*F or so the flow through the tanks will increase and heat transfer will speed up. Remember, the 150 degrees that the valve needs to see before it begins to allow return flow is coming from the supply line of the wood boiler, not from the return line from your tanks/zones. That is why there is no point in turning on your boiler pump until the boiler temp is up to at least 160. Normally, of course, you won't let your tanks get down as low as 100*F, so this flow issue won't be such a big deal. If everything is plumbed correctly, just keep chucking wood into the boiler and eventually the tank temp will start to come up where you want it.

 

[DaveBP]

Any idea what your heating load total is between your garage and house? BTUs per hour or per day.
Are your buried lines to the house single 1" PEX? How long round trip?
Has the setup been keeping the house warm on really cold nights (assuming you've had some cold nights since you've been up and running)?

 

[Fred61]

When the temperature reaches 150 you will see the rate of temperature accelerate. Before that, your mixer is only allowing a fraction of the return water through the return inlet of the boiler.

 

[markburtenshaw]

with a Termovar-type mixing valve at your boiler it will take a LONG time to get those tanks up to temperature for the first time. I would expect that once you see return temperatures above 100*F or so the flow through the tanks will increase and heat transfer will speed up. Remember, the 150 degrees that the valve needs to see before it begins to allow return flow is coming from the supply line of the wood boiler, not from the return line from your tanks/zones. That is why there is no point in turning on your boiler pump until the boiler temp is up to at least 160. Normally, of course, you won't let your tanks get down as low as 100*F, so this flow issue won't be such a big deal. If everything is plumbed correctly, just keep chucking wood into the boiler and eventually the tank temp will start to come up where you want it.

I guess that is not how the manufacturer told me to pipe mixing valve. if you look at the pdf spec it has the cold return from the tanks going to the 150 thermostat side of the mixing valve.

 

[markburtenshaw]

Any idea what your heating load total is between your garage and house? BTUs per hour or per day.
Are your buried lines to the house single 1" PEX? How long round trip?
Has the setup been keeping the house warm on really cold nights (assuming you've had some cold nights since you've been up and running)?

The house is rated at 38,000btu.
I have insulated 1" pex lines buried 5' underground one way trip is 120'
I can keep the house warm, it is set at 19 deg C

 

[maple1]

That's a big boiler, it should heat that storage no problem. It must be idling a ton? Seems to be something fundamentally wrong. Take lots of pics of your system & post them, also post more details of the piping/pumping between the boiler & storage.

 

[markburtenshaw]

When the temperature reaches 150 you will see the rate of temperature accelerate. Before that, your mixer is only allowing a fraction of the return water through the return inlet of the boiler.

I guess that is the initial struggle, if the tanks were so low to start it will take a long time to get them up to 100+. I guess my question is still how do I even get the tanks upto the 150 if the mixing valve is designed to only open up at 150? At 100 its still closed and only allowing the boiler to re-circulate?

 

[markburtenshaw]

That's a big boiler, it should heat that storage no problem. It must be idling a ton? Seems to be something fundamentally wrong. Take lots of pics of your system & post them, also post more details of the piping/pumping between the boiler & storage.

I don't idle at all, fan stays on high speed for duration of me loading it with wood. I will take some pics tonight and post them. I must be doing something fundamentally wrong I guess. I was told to try to keep the boiler temperature at 180 to 190 if I'm heating storage tanks, but at the same time was told to not let my (return) delta grow larger than 30 degrees otherwise risk boiler shock. So does that mean once the boiler is at 180 I should turn on my storage tank pump and let it circulate until the boiler temp drops to 170? or do I keep doing what I'm doing and try to keep it in the 180 range all the time?

 

[maple1]

Something is very messed up here. A 300,000 btu boiler hooked to a 30,000 btu load burning for weeks can't bring storage up to temp and doesn't idle? That's almost physically impossible.

 

[markburtenshaw]

Something is very messed up here. A 300,000 btu boiler hooked to a 30,000 btu load burning for weeks can't bring storage up to temp and doesn't idle? That's almost physically impossible.

Ha ha sorry should have clarified that a little more. The system has been operational for a few weeks but I have only burned 5 times during those weeks, as an estimate I've burned about 30hrs worth (at 180 deg F) Sorry, that would've been helpful.

 

[maple1]

Ok-that changes things a bit. When I heat mine from cold it takes a handful of burns. But you boiler is twice the size of mine. But your storage is three times the size. It will take a while.

 

[maple1]

Some quick off the cuff math tells me it will take 7 full loads of wood to raise your tanks 100 degrees. With no heat going anywhere else.

An IR temp gun will likely come in handy here too....

Edit: off the cuff revision, 5 loads.

 

[markburtenshaw]

Ok-that changes things a bit. When I heat mine from cold it takes a handful of burns. But you boiler is twice the size of mine. But your storage is three times the size. It will take a while.

Some pics

 

[Fred61]

I guess that is the initial struggle, if the tanks were so low to start it will take a long time to get them up to 100+. I guess my question is still how do I even get the tanks upto the 150 if the mixing valve is designed to only open up at 150? At 100 its still closed and only allowing the boiler to re-circulate?

There should be a bypass from the output of your boiler to the mixing valve that allows the valve to sample the output temperature. The second job assigned to the bypass is to activate (open) the valve enough to allow a small amount of return water to pass to the boiler return.

Looking at the schematic of the unit above you should have a bypass pipe coming from the boiler output line connected to port B of your mixing valve. That's the guy that will supply everything you need for the valve to read the temperature and also activate the internal mechanism.

 

[Fred61]

You posted those photos while I was typing. Hard to tell which pipes are which but first thing I think I see is a bypass around the valve. A little confused right now. Appears to be too many pipes connected.

 

[henfruit]

What size pipe did you use from the boiler to the tank?

 

[Clarkbug]

Hmmm something seems funky. Im trying to figure out the pumping/piping arrangement you have in your schematic. First impression is that the return protection valve needs to be moved some, but I think I see what is supposed to happen.

P1 should cycle based on the aquastat at the top of the boiler. P3 runs when there is load anywhere, and its just trying to pull from the boiler. When the water is cold, the valve opens so that it just circulates the underground loop. When above 160, it starts to open to allow some through, which is then sucked out of your primary loop by P2 and put in storage.

Simply put, you have a LOT of water, and a lot of uninsulated piping/steel to try and heat up. As maple said, at least 7 loads, more than that because you are heating your house/pipes/basement.

 

[markburtenshaw]

Some quick off the cuff math tells me it will take 7 full loads of wood to raise your tanks 100 degrees. With no heat going anywhere else.

An IR temp gun will likely come in handy here too....

There should be a bypass from the output of your boiler to the mixing valve that allows the valve to sample the output temperature. The second job assigned to the bypass is to activate (open) the valve enough to allow a small amount of return water to pass to the boiler return.

Looking at the schematic of the unit above you should have a bypass pipe coming from the boiler output line connected to port B of your mixing valve. That's the guy that will supply everything you need for the valve to read the temperature and also activate the internal mechanism.

That is how its piped right now, I didn't realize or my understanding was port c wouldn't open at all unless there was 150 deg water there. so you are saying if water temp at port C is 100 deg and port B is 180 then port C will slightly open and allow water through to mix with port B? if so my worry is it will not be enough cold water through to even load down the boiler and I will go in to idle mode and lose my efficiency?

 

[Clarkbug]

Most likely, yes, you will idle with your current setup until the return water temps begin to rise. (If Im following it right...)

 

[markburtenshaw]

What size pipe did you use from the boiler to the tank?

Boiler to tanks is 1 1/4" pipe

 

[henfruit]

I looked at the drawing. If you are using 1.25 pipe from the boiler to the tank, it is to small. You need to move 30 plus gallons a minute for that size boiler. What brand is the mixing valve?

 

[henfruit]

1.25 is good for a 40 kW boiler.