Dual feeds to storage

[NCPABill]

Thanks to all who have posted - the aggregate field of information on Hearth.com is huge!

I'm upgrading to gasifier soon and my question relates to storage. I currently have hydronic baseboard heat, which I heated with a wood boiler (1978 model), or switched to my natural gas boiler (an either / or situation - no control connections). Now that I'm planning storage, with the understanding that I will use natural gas as a very limited backup, I'm wondering if I can simplify my system so that my gas boiler would feed the storage tanks in the event of: 1. gas boiler being turned on and 2. thermostat on tanks calling for heat.


Thanks in advance for your time - I know by reading for the past year or so that many of you dedicate enormous amounts of time here.

Bill

 

[jebatty]

I don't see any technical reason why you could not do this, but I think the issue relates more to what is the most efficient way to use your NG backup boiler. In other words, is it more efficient to have longer burns with excess btu's to storage, and then draw from storage until the next burn; or to have shorter burns, bypass storage, and just use for immediate heating needs. Part of the answer may relate to storage losses and whether or not those losses are efficiently used in a heated space.

 

[jimbom]

...or to have shorter burns, bypass storage, and just use for immediate heating needs....

This was my initial thought also.

 

[ewdudley]

I'm upgrading to gasifier soon and my question relates to storage. I currently have hydronic baseboard heat, which I heated with a wood boiler (1978 model), or switched to my natural gas boiler (an either / or situation - no control connections). Now that I'm planning storage, with the understanding that I will use natural gas as a very limited backup, I'm wondering if I can simplify my system so that my gas boiler would feed the storage tanks in the event of: 1. gas boiler being turned on and 2. thermostat on tanks calling for heat.

Works well for us. We have a fossil fuel boiler in parallel with the wood boiler and both feed the top of storage. When top of storage aquastat calls for heat at a temperature below the depletion-of-storage-temperature then the fossil fuel boiler kicks-in.

To avoid short-cycling the fossil fuel boiler call-for-heat signal is extended with a delay-off timer so that once the fossil fuel boiler starts it runs for at least a certain amount of time, thirty minutes in our case, pick whatever number you want. Thus only a small part of the top of the storage tanks gets heated and the inefficiencies of short-cycling are avoided. As you suggest, it's nice and simple in that the rest of the system just draws heat from storage and it doesn't matter to the rest of the system where the heat came from or what mode the boiler side is in.

However since the the back-up boiler is non-condensing, we needed to add return temperature protection since the bottom of storage is only 110-115 degF.

--ewd

 

[NCPABill]

Thanks for the fast responses. There is So much information to digest. Essentially, the natural gas boiler may get used two days per year, like in the go-see-someone-for-a-weekend situation. If we're lucky, a little warm weather with the thermostats set down a little, maybe never!

Thanks again. Anyone find a plumbing diagram laid out like this anywhere?

Bill