Trouble getting storage up to temp

[Fred61]

But if you set your launch temperature to 185 degf or so then there will only be one lap through storage. When the 185 degF water comes back around storage will be filled from top to bottom with 185 degF water and you'll be stuck right where you want to be. When my system gets to this point I don't idle, I just shut the combustion fan off and let the fire go out.

That is exactly the theory and numbers I use but in reality it hasn't worked out for me in practice. I actually launch at 187 but soon after the center temperature drops about 4 degrees. which means I'm mixing even after all my efforts to keep it from happening.

 

[Fred61]

First off THANKS I knew you guys would have have some great thoughts.
Since my valve above the Danfoss is wide open currently, that is the first thing I will adjust. Will also take a quick look inside the guts of the Danfoss to make sure everything looks OK. I searched around and found the thread about drilling a hole in the brass plate of the thermostat might try that also.

I would suggest you stay away from your Danfoss for now. I don't think your problem is there. Drilling a hole will only dilute your bypass water and will defeat the accuracy of the Danfoss. I think it will be like taking apart your pocket calculator to see why it's giving bad answers.

 

[easternbob]

Is that why my calculator isn't working any longer
Good point I'll try one thing at a time.

 

[maple1]

I also think I would leave that other bypass going around the Danfoss closed. Actually not sure exactly what its intended purpose is. Main thing in all this is to maintain boiler return temps above 140 - but not a whole lot above with cold storage. Won't be an issue with bottom of storage at 150, but could be if it gets down to say 120.

 

[Fred61]

Shut the Danfoss bypass off completely. It's not good to allow flow when return water is cold and is not needed when return water is above 140. Experiment with the valve in the system bypass that goes to the center tapping of the Danfoss. You only need a little flow in order for the sensor bulb on the thermostat to sample the water temperature and open the gate. We talked about system resistance vs bypass resistance in a conversation here not more than three weeks ago.

 

[hartkem]

I have a similar setup with a eko 40 and 500 gallons of storage in my basement. My boiler is further away at 150' but I am using 1.25 thermopex vs your 1 inch. I also have a danfoss valve on my system. My launch temp is maxed at 170 with hysteresis at 2. I can only get the top of my tank to about 185 when the boiler is 195. Unlike you though I can get the bottom of the tank to about 183. I had issues with the boiler going to idle mode frequently because I was over pumping with the taco 0011. My tank does not have chambers inside nor any diffusers. The supply enters top of tank and return is on the bottom about 3.5 feet down on the same side. The high velocity of the water would cause an internal current in the tank which would basically cause the hot supply water to bypass directly out the return back to the boiler. I switch the pump to a much smaller 3 speed taco 00R which has completely resolved that issue. I run the pump on high speed. The boiler won't idle until the top of the tank is 185 and bottom about 175. After idling a few minutes the boiler starts again and continues to push the bottom of storage to about 183 which is the highest I have seen. Not sure it is realistic to get remote storage to the same temp as the boiler, however, you should be able to get the bottom temp higher than you are.

 

[leon]

I still think your not going to solve the issue unless you
pump continuously from the storage to the boiler in
a closed loop.

By using the three speed pump on the lowest setting to
heat the house drawing off the storage tank with a
side arm heat exchanger and returning the cooler water
back to the tank.

 

[mr.fixit]

I also think I would leave that other bypass going around the Danfoss closed. Actually not sure exactly what its intended purpose is. Main thing in all this is to maintain boiler return temps above 140 - but not a whole lot above with cold storage. Won't be an issue with bottom of storage at 150, but could be if it gets down to say 120.

I think that lower bypass is put in to bypass the danfoss for freeze protection,as in boiler off but circulation pump running to constantly circulate the water.

 

[easternbob]

Well I'm happy to report I was successful last night. I throttled the valve above the Danfoss way down and it made a huge difference. For 4 years I had left that valve wide open and heated the house just fine, never noticed the by-pass flow because the heat load was being easily met.
I would estimate I have the valve closed 3/4 of the way and will continue to adjust to hit that sweet spot.

lower bypass is put in to bypass the danfoss for freeze protection

That is correct. If we go away for a week during the winter I can flow water from the boiler into the house and back to keep things from freezing up. I did shut that lower by-pass around the Danfoss completely

Thanks again for all the comments/help!

 

[maple1]

I still think your not going to solve the issue unless you
pump continuously from the storage to the boiler in
a closed loop.

By using the three speed pump on the lowest setting to
heat the house drawing off the storage tank with a
side arm heat exchanger and returning the cooler water
back to the tank.

I read that 5 times & still couldn't figure out what you were saying.

And on the first part, if he pumps continuously in a closed loop from storage to boiler he loses boiler return temp protection.

 

[ewdudley]

I think that lower bypass is put in to bypass the danfoss for freeze protection,as in boiler off but circulation pump running to constantly circulate the water.

Nice. I guess the old drill a small hole in the valve plate trick is supposed to do this, but the bypass seems much more on point. We should get in the habit of drawing a bypass in our system sketches.

 

[Fred61]

I believe the hole in the thermostat plate originally was to equalize pressure on both sides as many have a small hole originally from the factory.
I recall discussions here about drilling a hole but I don't recall what the subject was.

 

[velvetfoot]

We should get in the habit of drawing a bypass in our system sketches.

Are there advantages other than freeze protection for an outdoor installation? Maintenance? I think I could've used one when flushing/filling/purging, but not sure about now.

 

[leon]

After reading it I agree i did a poor job of explaining it.

What I should have said was:

One very small pump should be used to feed the nurse tank with hot water from the boiler
with a gravity drain to the boiler sump from the bottom of the nurse tank.

The second smaller pump should be used to pump the hot water in the nurse tank through
the side arm exchanger with a third "small" pump heating the home.

One pipe steam is so much simpler.

 

[easternbob]

That's kind of what I have.
A pump on the back side of the boiler to send water to storage. BUT before that water makes it to storage it goes thru my side arm on the DHW tank (didn't show this on my diagram to keep things clear and simple).
There is a seperate pump that then draws water from storage and sends it to my primary/secondary loop to feed the house heat demand.

 

[Woodfarmer1]

I still think your not going to solve the issue unless you
pump continuously from the storage to the boiler in
a closed loop.

By using the three speed pump on the lowest setting to
heat the house drawing off the storage tank with a
side arm heat exchanger and returning the cooler water
back to the tank.

What is the reason to use the lowest setting on the pump?

 

[leon]

What is the reason to use the lowest setting on the pump?

Smallest volume of hot water exiting the boiler at all times and keep the water temp up in the boiler at the same time.

 

[goosegunner]

Smallest volume of hot water exiting the boiler at all times and keep the water temp up in the boiler at the same time.

I think that would increase his idling problem.

I had issues with my boiler doing the same thing, I increased flow and that created the multiple lap scenario. Without variable sped pump and fan controls it is difficult to match the flow and output to a consistent pattern. I have started using larger splits of wood and I have had less issues with idling and also smoke explosions have been eliminated.

gg

 

[easternbob]

Well it's been almost 20 days since I throttled down that valve going to my Danfoss and things are working great. The other day I had my storage up to 199 deg, although that were a bunch of idiling involved to get that high (made the mistake of adding too much wood...)
The pump on the back of my boiler is single speed TACO 009 so I don't have the choice of high, med, low but I have to agree that quicker I pump heat away from the boiler the better I wouldn't want to slow it down or other wise it would idle. That was kind of the problem I was having when the Danfoss was allowing too much water to 'recycle' and not go to the storage.

 

[goosegunner]

Well it's been almost 20 days since I throttled down that valve going to my Danfoss and things are working great. The other day I had my storage up to 199 deg, although that were a bunch of idiling involved to get that high (made the mistake of adding too much wood...)
The pump on the back of my boiler is single speed TACO 009 so I don't have the choice of high, med, low but I have to agree that quicker I pump heat away from the boiler the better I wouldn't want to slow it down or other wise it would idle. That was kind of the problem I was having when the Danfoss was allowing too much water to 'recycle' and not go to the storage.

Glad you got it figured out!


Anyone know the limits of Thermopex or logstor with 200 degree water?

I have copper to storage and then 20' of copper to underground Logstor. I seldom go over 190 as a precaution.


gg

 

[Fred61]

I've overfed my wood chamber two or three times already this year. It was a waste of wood and a smoke generator since the wood is not converted to charcoal when the boiler first idles. Good way to muck up the stack. I need to light a fire every day regardless whether storage tops out at 172F or 182F so I still don't know why I add those last two logs to the fire.

Anyhow, I'm glad you got it sorted out. An easy answer to a complicated problem.

 

[maple1]

I have stopped putting that last half load or so of wood in - so far this winter at least. So it's been quite a while since I've seen over 180 on my storage. Even when I was charging storage up there, it was very rare to see 190. Should see some wood savings by the time winter is over, hopefully - getting that last 10 degrees seems to take the same amount of wood as the 20 degrees before it. And I will still need to burn the next day anyway.

Time to go light up....