Control of boiler and storage

[Robby]

I need help.

I just purchased a 1100 gallon pressure tank for hot water storage. I can't fiqure how to hook up the controls. My boiler now has control that opens draft at 170, closes at 180, dumps heat (120,000 btu zone) at 200. Second control starts circulation pump at 190 to move water from boiler,(42 gal) to present storage 120 gal. The second control is my idea, works fine. When boiler at idle heat slowly builds up in boiler water and a short 3 or 4 min run moves to storage.

I had planned to run line from boiler to stoage tank and return, then seperate lines from tank to house. I can't fiqure how to hook up controls. I only want boiler to tank pump to run when boiler fired, but stop when boiler out.

How do I do that?

thanks
Robby

 

[Nofossil]

I need help.

I just purchased a 1100 gallon pressure tank for hot water storage. I can't fiqure how to hook up the controls. My boiler now has control that opens draft at 170, closes at 180, dumps heat (120,000 btu zone) at 200. Second control starts circulation pump at 190 to move water from boiler,(42 gal) to present storage 120 gal. The second control is my idea, works fine. When boiler at idle heat slowly builds up in boiler water and a short 3 or 4 min run moves to storage.

I had planned to run line from boiler to stoage tank and return, then seperate lines from tank to house. I can't fiqure how to hook up controls. I only want boiler to tank pump to run when boiler fired, but stop when boiler out.

How do I do that?

thanks
Robby

An aquastat would typically be used for that purpose. Do you have a place to mount one on the boiler? Typically it would come on at a much lower temperature - perhaps 160 or 170.

 

[Robby]

Second control starts circulation pump at 190 to move water from boiler,(42 gal) to present storage 120 gal. The second control is my idea, works fine. When boiler at idle heat slowly builds up in boiler water and a short 3 or 4 min run moves to storage


That is a second aquastat I installed. If it starts pump at a set temp, why would it not continue to run pump, after boiler goes out until temperature in storage comes below set point. I still don't understand?

Robby

 

[Nofossil]

Second control starts circulation pump at 190 to move water from boiler,(42 gal) to present storage 120 gal. The second control is my idea, works fine. When boiler at idle heat slowly builds up in boiler water and a short 3 or 4 min run moves to storage


That is a second aquastat I installed. If it starts pump at a set temp, why would it not continue to run pump, after boiler goes out until temperature in storage comes below set point. I still don't understand?

Robby

You'd want it to be mounted on the boiler, not the storage tank. When the boiler temp drops, it shuts off.

Maybe I'm not understanding the problem. Any chance you can post a plumbing diagram?

 

[WoodNotOil]

If I understand what you are asking, I think a set point differential control might be a good solution. They have a sensor for the storage tank and one that could go on your boiler. You tell it what temp to get the tank to and how much hotter the boiler should be than the tank temp and it turns the pump on/off to accomplish charge. There are several commercially available that have been discussed here recently:

Azel 7772 (broken link removed to http://www.azeltec.com/catalog.0.html.0.html#DST-777)

Tekmar 156 http://www.tekmarcontrols.com/prod/156.shtml

Steca differential control https://www.hearth.com/talk/threads/29986/

 

[DaveBP]

I'd like to inject a word of caution into the discussion on differential controls that's going around the forum.

Some of the controls being proposed (particularly some of the Azels) are not necessarily "differentials controls" as much as setpoint (or two-stage setpoint) thermostats with digitally adjustable differential. The differential in this case being something like "overshoot and undershoot" but still at one particular temperature. I believe this is also referred to as hysteresis. Keeps things from short cycling back and forth too quickly.

Real differential control will activate whenever the temperature difference between 2 inputs is whatever you have set. Say, if you're shooting for 20F differential it will kick at 110/130 or 170/190. Very different function.

It's confusing to read the features of some of the controls and see the term "differential" so prominently listed. The big price difference is your first clue.

End of sermon.

 

[WoodNotOil]

I'd like to inject a word of caution into the discussion on differential controls that's going around the forum.

Some of the controls being proposed (particularly some of the Azels) are not necessarily "differentials controls" as much as setpoint (or two-stage setpoint) thermostats with digitally adjustable differential. The differential in this case being something like "overshoot and undershoot" but still at one particular temperature. I believe this is also referred to as hysteresis. Keeps things from short cycling back and forth too quickly.

Real differential control will activate whenever the temperature difference between 2 inputs is whatever you have set. Say, if you're shooting for 20F differential it will kick at 110/130 or 170/190. Very different function.

It's confusing to read the features of some of the controls and see the term "differential" so prominently listed. The big price difference is your first clue.

End of sermon.

What products do you suggest using for charging tanks?

 

[in hot water]

A true differential control, also known as solar controllers... They measure temperature in two locations and start a pump, valve, etc based on the difference. So, fo example when the boiler is 15 degrees warmer than the storage the pump starts. When the tank gets to within 5 degrees of the boiler it turns off. The range is adjustable, of course. The same control can be used to "un-load" the tank, again based on temperature difference.

Plenty of brands out there. Most models will have two, three, or more outputs in one control, digital display, etc. Caleffi, Resol, Stecca, Goldline are some of the common brands.

hr

 

[Robby]

A true differential control, also known as solar controllers... They measure temperature in two locations and start a pump, valve, etc based on the difference. So, fo example when the boiler is 15 degrees warmer than the storage the pump starts. When the tank gets to within 5 degrees of the boiler it turns off. The range is adjustable, of course. The same control can be used to "un-load" the tank, again based on temperature difference.

Plenty of brands out there. Most models will have two, three, or more outputs in one control, digital display, etc. Caleffi, Resol, Stecca, Goldline are some of the common brands.

hr

You know, that's an option I had not thought of. I have a solar controller (on solar system) and thats exactly what I need. One of the measurements will be chimney temp. No heat, pump off.


Thanks

Robby