Gravity able dump zone with radiant floor system

[Dfmihm]

Currently, my whole home is a radiant floor heat with pex. 2 zones, 2 pumps, and my current “dump” is hooked to the larger zone. Now bears the question of what do I do if the power goes off? Yes I do have a generator and can witching a short time have my whole system running off of such, but then of course if I’m at work and my wife needs to switch it over, is there a way I can incorporate a gravity fed zone or something that would at least keep the boiler from over heating? I’m not sure how radiant floor would gravity feed and nor am I really willing to try it without having any idea how. I know some folks talk about just simply flipping or turning a valve that their whole system will gravity feed, but I believe that is with cast iron or baseboard heat. I thought about just running a loop that was higher than my boiler, but I’m not convinced it’s that simple. That loop I mentioned would probably be fin tubing mounted in the basement and garage ceiling maybe 50 feet away and could be 3-4 feet above the boiler in height.

Any input would be helpful, and I did search this but really can’t find anything that is pertaining with the floor heating.

For some detail, I am running 2 mixer valves which keeps the floor water around 140-150 and usually the return water is around 120-130. With so much pex, tight turns, and just distance, I have noticed it is not a fast flowing system. Which is why I somewhat am concerned about allowing or thinking it will gravity feed.

Thank you folks!!

[nepacoal]

I had the same fear / issue when I ran my handfed. We had a power outage right as my boiler reached temperature and the temperature got scary high.

I put the boiler on an Aims inverter/ charger with a single 125 AH battery. Problem solved.

Now that I switched to a stoker, the same setup provides several hours of runtime which gives me plenty of time to break out the generator if needed.

[Richard S.]

I know some folks talk about just simply flipping or turning a valve that their whole system will gravity feed.....

There is typically going to be a flow control valve and one of the things it does is prevent gravity feed. On the top is a levered knob, at least on the B&G models. That can be opened to hopefully allow it to gravity feed.

This may or may not work but in my experience in two different houses with baseboard it can work too well. In one case it was left open accidentally and I woke up to 80 degree bedroom. In another case at another house it was malfunctioning after I had completed some work and the temp was going into the high 70's. Here is an example.

https://www.supplyhouse.com/Bell-Gossett-107034-3 ... ow-Control

[Dfmihm]

Yeah there is definitely not one of those valves in my system. Might have to look into this.

Wasn’t sure if the hot water temp and a steep return with the radiators and or baseboard being higher than the furnace if it would just naturally flow? I’m no physics expert obviously. Does hot water pull toward cooler areas or is it opposite? Just brainy questions.

Thanks for the responses though nonetheless!

[Richard S.]

Setting aside mechanical operations heat moves in three ways; convection, radiation and conduction. Hot water will rise through convection just like air if it has a suitable path.

[c&t coal]

I have the same system and each zone has a flow check valve located very close to the boiler. When I'm running the coal boiler, I leave the valves open to allow the migrating hot water to flow. Sometimes the house gets a little too warm, but usually the extra warmth is welcomed. When I'm running the oil boiler I return the valves to the normal position so that the burner doesn't run unnecessarily.