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Control Zones on old boiler system -retrofit

Hello All,

I just purchased an older 3,700 sq ft home with a newer 90+ boiler. However the system is not automated zoned as it has several cast iron registers with manual valves. I do plan on adding a few new circuits to the addition/wings of the structure but would like to avoid re-plumbing the majority of the house to have it properly zoned.

Is there a way to create multiple zones in the house without running individual circuits/loops back to the boiler? Preferable an retrofit-able electric valve that can be added at the register and controlled by a zoned T-stat

I was thinking of building my own automated control valve retrofit to install at the 1st register in each zone. However, I have to believe there is already a device out there and with better finish then what I would come up with. Just how do you take a zone control valve and dress it up? - we leave that one until I decide I have to DIY


Re: Control Zones on old boiler system -retrofit


Yes there are such valves.

You say BOILER and ZONE VALVES, CAST IRON, so I assume you have a forced hot water system?????

The most likely candidate for the purpose of what you describe in your post is called a Thermostatic Radiator Valve (TRV)---the good news is that they require NO ELECTRICITY to operate and are relatively low-cost---the bad news is that it would depend on how your radiators are PIPED (piping arrangement) as to whether you would be able to use them.

Since you describe the cast iron registers as having turn-off valves on them, I wonder why you are not getting sufficient temperature control by simply turning up or down the register manual valves???

If your present manual valves are inoperative or inefficient, then it DOES sound like you have the proper piping to use a TRV---the "high performance" site below illustrates the different piping arrangements that exist in hot water systems---with the first example (the series one-pipe) you CANNOT use an on/off valve at the radiator, since to do so would shut off the water for all subsequent downstream registers.

The other piping arrangements at the site list a one-pipe monoflow piping arrangement, and several two-pipe arrangements---a TRV could be used for all of these piping arrangements---which piping arrangement do YOU have???

You will have to do some detective work & draw a little diagram of how the hot water flows thru your system---start at the boiler---the MAIN SUPPLY pipe comes out of the top of the boiler (usually a 1 1/4" large pipe that may feed several loops that you can see in the boiler room; the main pipe then eventually returns back to the lower side of the boiler as the MAIN RETURN PIPE.

Hopefully, you will be able to see most of the heating piping in your house, if it's not hidden behind walls & floors.

TRVs are made by Danfoss, Honeywell & others & cost approx $50 ea.---check patriot supply & pex supply for online prices.

There is an ingenious wax-like material inside the valve that liquifies at different temps & thus can open & close the valve as it acts as a thermostat.


Re: Control Zones on old boiler system -retrofit

Thanks for the quick reply. I just got back from the house and really don’t want to make plumbing the heating system a priority.

The house has several parallel loops. I was actually hoping for electrical instead of thermo dynamic however I will still investigate them.

We have not tested the system yet as its still winterized so no problems are known. I’m just use to having several zones all w programmable T-stats.

Our plans are to add a water heater before we move in and a wood boiler next year. Since the boiler is a 2-3 year old Weil-McLain I was thinking towards an indirect water heater. My thoughts were to create an on-call system with all of the zones along with future radiant floor heating in 2 baths, kitchen and rec room along with demand heat for the water heater only.

Other then the water heater the heating system is not an immediate issue. I’m concerned the real answer is to replace the steel pipe with copper along with a well layout manifold. I’m now coming to the conclusion to install a used water heater immediately. Focus on some electrical and window upgrades along with insulation and a boat load of maintenance. Come back to the heating system next year with the wood boiler addition, indirect water heater and all new plumbing.

I guess the real question it to re-plumb or patch.

Now here is another thought.
Go with the TRVs
Create a smaller # of zones manifold w/
Zone 1 – whole house heat controlled by master thermostat with several TRV
Zone 2 – indirect water heater,
Zone 3 to feed radiant floor heat- lower tempature/ mixing valve – could I have sub-zones here????
And finally means to tie back the wood boiler.



Re: Control Zones on old boiler system -retrofit

PM issued.

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