Converting a single zone 2-pipe hydronic heating system to multi-zone

rfriedman

I wish to multi-zone a single zone hydronic 2-pipe heating system that cast iron radiators with 1” angle valves.

I have been looking at a Shelly TRV.

Shelly claims that their TRV also controls the boiler (I presume circulation pump). I have used Shelly’s WiFi relay to close the connections on my hall thermostat, so I expect that is the intended method.

My home has several rooms each with at least one cast iron radiator. I wish set up each room as its own zone with a thermostat and appropriate radiator valves. This will place a variable flow demand on the circulation pump. I intend to address this issue using a smart circulation pump.

If this valve path is not achievable, I am considering using a thermal actuator, plus all the wireless relays and power supplies to make this happen. I would like to know if these actuators directly connect to TRV’s or will I have to make some adaptors.

Speaking about making adaptors, I have already built a system by modifying an off the shelf $18 radiator valve, making it a ¼ turn action and adapting a ¼ turn ball valve motor. I set it up to run a cyclic endurance test with a circulation pump and relays, to make sure the valve seals and other non-standard components survive but quickly came to the conclusion that the ball valve motors make too much noise for domestic applications. Also, by the time I make all the adaptions to my $18 radiator valve, it hardly competes with an off the shelf Thermostatic Radiator Valve.

Clearly, I am a novice at all this with enough background to make me dangerous. I would all the advice you can give me to steer me in the right direction and keep me out of trouble.

Ironman

What type of boiler do you have? What’s its btu rating? How well is it matched to the heat loss of the house? Have you done a Manual J heat loss calculation or a radiation survey?

hot_rod

There are a few way to use TRVs with a delta P circ and operate the boiler

A flow switch, an induction relay, or a pump that has a switching capability

Then you could have room by room temperature control.

Do a load calc, see how the boiler and radiators match the calculated load

Too much zoning could cause short cycling issues

rfriedman

My Boiler is rated at 118 BTU/HR. I couldn't find a usable online J calculator, and probably do not have the background to do a qualified calculation. I will tell you that the boiler can bring the house from 62-68 on a cold winter day in about an hour.

The boiler was sized by a qualified plumber and I assume it matches the load requirements with all the radiator valves open. I think the Delta P circulation pump will cover my flow rate, but I share the concern about short cycling the boiler. Am I correct in thinking the short cycling results is switch wear and more off peak performance usage?

Ironman

How about posting some pics of the boiler and its near piping?

How old is your house and how many square feet?

Here’s a chart from which you can do a radiation survey. By determining the total square footage of your radiators (EDR), we can see how closely they’re matched to the size of your boiler.