Add-On Insulated Boiler Water Storage System

I believe that you can really stretch the capacity of a smaller boilers, if you added an insulated Boiler Water storage system. This would give you more storage capacity when the call for hot water to the baseboard is requested. And the water temperature would be maintained when the house is not calling for heat. Any recommendations on the tank, design and has anyone done this? I also believe the tank can also include bypass valves to eliminate in warmer months.

These storage systems are used quite often with woodburners as they need to run very hot to be efficient. I don't think there is much need for them with coal boilers and they are not cheap.

More on the subject here, just do a search. https://www.hearth.com/econtent/index.php/forums/

You can improve the efficiency of an OVERSIZED boiler with storage

but its the opposite with an undersized!

Almost a detriment as you are effectively adding additional load to an already stressed appliance!

I believe you are mostly correct, maybe completely correct. I burn bit and wood. I change draft setting according to quality of wood and of course much less draft for coal. I cannot comment about burning anthracite, never done it, not available. But with bit, my bit, if draft is set to get maximum BTU output I have a clinker problem, over-run of boiler temps (not a serious problem) and I believe much less efficiency. After much testing I found an ideal draft setting where it appears to be most efficient and very few or no clinkers. Storage averages out the demand.
If you notice there threads where they are trying to reduce the output of boiler, making firebox smaller etc., as it is too large when temperatures go up. Storage allows you to let boiler go out, maybe only fire every few days. I think that re-firing anthracite is not as easy, I can re-fire bit in 20 min. Wood of course same problems, just larger. I added 180 gallons inline storage, worked better. Now I am adding 1200 gallons, using a differential controller between boiler and storage. Also heating circuit will come directly from storage, not via boiler. I have added 60 tube solar for DHW in summer,and it dumps excess BTU into the storage tank. Not costing as much as you may think. Complete system, tank,insulation,extra pump, etc. about $2000.00

Robby

You can improve the efficiency of an OVERSIZED boiler with storage
but its the opposite with an undersized!
Almost a detriment as you are effectively adding additional load to an already stressed appliance

Somehow we are confusing two different issues. First oversizing decreases the efficiency of the unit. While an undersize may not be carry the load it is probably at the optimal efficiency. Simple law of physic just as a small car with a small engine works harder and get better mileage. And large car with an oversized powerful engine does not. In a small car you don’t have the power but you have the efficiency.

My original question has nothing to do with efficiency it was more about storage and demand. The quote

“Storage average out Demand”

is right on the money.

A small unit is not necessarily a stressed appliance. It is an appliance at present storage capacity which cannot keep up with demand. But over the average of a day with additional volume of heat water it can even out the peaks. I don’t believe you need 1200 gallons but and additional 80 gallons will do the trick. I find this to be true with zoning also. Adding zoning is like adding 20% more capacity because not all zones are calling for heat at the same time. You are tricking the system to allocate load more effectively.

By the same means adding a heated insulate tank increase the water volume needed for satisfying heating during peak demands with a smaller unit. During the peak time the smaller unit is bringing the storage tank up to boiler temperature.