Thoughts on electric / gas boiler hybrid

clammy

I was dreaming and thinking two bad things at once and wondered why no manafacturer has came up w a combo unit which uses both gas and electric .Gas on the design and electric on shoulder or for extremely small load .i know it sounds crazy but I think it would be better then short cycling a cast iron or mod com on extremely low load like small radiant , I m not saying electric for hi temp system more for low temp / low load scenarios just to prevent cycling espically on mods w a 30 degree setting till she re fires is a total waste and never does a great job of assuring even heat . I know a buffer tank could be added but sooner the later u will be back to firing the boiler hitting the limits and waiting .any thoughts peace and good luck clammy

Zman

I think it depends on your energy costs. Where I am electric is 4X-5X the cost of natural gas. Even with bang/bang boilers the gas is the clear winner. I do think we will see air to water heat pumps taking the stage as the "net zero" movement gains momentum. The perfect hybrid would have the heat pump run on moderate and shoulder days with gas taking over on the peak days. Kind of an expensive install though...

The Steam Whisperer

I've used electric water heaters as my buffer tank . This gives me electric heat back up and I can use electric in the buffer seasons. The other possibility is to use a large diameter pipe in your supply with a tee on the end which you can screw your electric element into and wire it to come on during light loads and then shut off when the loads increase.
Gas and electric are getting closer here in Chicago. The gas company base charges and the additional charges for rebuilding the piping grid have gotten so high that they account for about 40% of our highest midwinter gas bill ( gas piping is getting replaced that should have been replaced around WWII). Overall cost for electric is only about 2x that of gas with the price of gas running about $0.35 per therm and electric about $0.10 per KW, exclusive of all other charges which jack up the cost.

hot_rod

I thought HTP and Bradford had tanks with burner and electric?

Solar tanks have hydronic coils and electric, BW has some gas fired solar coil at bottom with burner mounted up high. Some had the burner at the bottom but the aqua stat in the upper 1/3 of the tank.

I’ve seen some HX wands that drop a small HX into any water heater, common in UK, but with metric threads

Solid_Fuel_Man

I'd like to see some mod/cons with a low input equivalent to a burner on a stove. 5,000 btu/hr isnt much, and would prevent short cycles in most system or a small buffer.

I've also done the electric water heater thing, but used to 1" threaded ports where the elements went for pipe connections.

I have seen, but not done m it self guys used the iron T method and install a water heater element into an extremely low value electric boiler of sorts.

Resistance electric just isn't cost effective most (if any) places. And the reality that equipment is lasting pretty long as it is.

Electric resistance is about the best backup heat anyone could ask for though. Cheap install, zero maintenance and can sit indefinitely and you know it will work as long as there is power.

GroundUp

I did build a hybrid of sorts once upon a time using the element in the run of a tee method and a Takagi tankless in a hunting cabin. Bathroom/mechanical room had the well equipment and needed to stay warm while the rest of the cabin was left to freeze during winter so the single loop of radiant didn't meet the flow requirements for the Takagi to make the flow switch. Single 1500W element wired in series with the circ for that zone but broken by an aquastat when the Takagi water was hot, still works like a charm 7-8 years later. I've done a number of the same setups with outdoor wood boilers as well, as they are typically constant circ and a simple strap-on aquastat or Ranco controller on the supply line will light up the element(s) when the supply water falls below X temp (40 degrees for freeze protection). My own OWB at home uses a single 4500W element and a 240V Ranco set to 40-42 so I can shut it down when I go on vacation instead of relying on the neighbors to feed it. Been that way 4 years now

Lance

Electric has its advantages. I replaced an outside oil FHW boiler in a summer vacation home that had a failing chimney. They even put the electric water heater in the same room outside the building envelope. They unit could freeze quickly without power. A quick heat loss calculation showed the boiler system oversized. Abandoned the old boiler. Re-piped the supply and return into an interior closet with a wall hung electric boiler. All controls fully accessible in the space of a medium suitcase. Placed the water heater in an interior closet. No more oil; oil tank; chimney; needed. no more oil burner, soot maintenance. Silent comfort restored. Cost to operate. Less than the old. Homeowner: Very happy.