Radiant Heating Zoning

Kevin Polka

I have a customer using tankless heaters for his radiant heatig system. The house is about 2500 ft2 and has a total estimated heat loss of about 78,000 Btu/H. He is looking to put three to four zones on each floor (three to four thermostats) while insulating all interior walls and putting in well insulated solid interior doors. How would you control this system; pumps or zone valves? Do you know of any system that has multi thermostats and a main thermostat for each floor (during the day the main thermostatb would be in control but at night when your sleeping and the doors are closed the individual room thermostat would then take over control?

hydronicsmike

This almost sounds like...

...what our brothers and sisters in the UK are doing, but the other way around. There, they have thermostats for each zone to maintain different temperatures throughout the day, while the main thermostat is set way high (so its always calling) allowing the individual zone thermostats to limit the temperature for each zone. Then in the night, the Main thermostat is set low (to a temperature desired during for setback), which will now limit the overall building temperature.

Basically, the main thermostat enables the zone thermostats while it is calling through a N/O contact while it is set high. During the night, the main thermostat is set low and will disable the zone thermostats when it reaches its limit. I hope this makes sense. They usually use a single programmable thermostat to accomplish setback for the whole house.

Sounds a little complicated and in my eyes, not all that great and advanced.

Where did I hear people say that most everything in our industry is more advanced in Europe??


Make it simple and either use all programmable thermostats for each zone and set those up, or have a look at the tekmar Zone Control 369 with the 062 RTUs in place of thermostats. You'll be able to set an Occupied (Day-time) temperature for each zone and and UnOccupied (Night-time)temperature. A single timer built right into the Zone Control will then automatically switch from Occ to UnOcc temperatures. Doesn't this sound simpler or more advanced?

Drop me an email, if you feel I can help you with anything. I'd be happy to.

Thanks,

Mike

Mike T., Swampeast MO

In the UK...

...are they doing this with TRVs on the radiators and a "master" t-stat set high to keep circulation during the day and low to starve the TRVs during setback?

hr

Some of those

instantanous have huge pressure drops. As such high head pumps are the norm.

Be careful with zone valves and high head pumps, you will definetly want a PAB valve to calm things down as the zone valves open and close

hot rod

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tombig

To hr

For the last year I have followed all posts concerning gas fired instantaneous water heaters as hydronic heat sources. It seems that the general consensus is that they don't fit the application. Whether venting, code, approval rating, or flow issues, I haven't felt comfy enough to install.

You are truly the 'McGuyver of the wallies. Any input?



As always, "Thanks in Advance"

hydronicsmike

Mike T.

Believe it or not, I have seen a few of those systems there where they used a Main Thermostat with a built in Timer and the Zone Thermostats for the individual Zone Control. During the day, the main Thermostat is set high and all other thermostats are enabled so that they could cycle or operate the individual zone devices (Pumps or Valves). During the night, the Main Thermostat is set for a lower temperature for setback. Now every time that Main Thermostat is satisfied, all Zone Thermostats are dropped out.

Its typically done via switching from a N/O to N/C contact within this Main Thermostat. It's a bit different than we do things, isn't it?

hr

Why use an instantanous

when there are so many "great" hydronic heat generators on the market?

ALTHOUGH last Sunday I went on a service call only to discover an 18 year old Paloma with a circ pump, 3 way Taco zone valve operated by a Goldline setpoint control for mix temperature control. Connected to SOLAROLL!!

Original owner hasn't touched a thing. The Taco is leaking around the stem o-ring.

The owner said to do what ever it needs to repair or upgrade. A this point I'm tempted to replace the zone valve, clean and combustion check the Paloma, and let 'er rip.

What are my choices with a slab full old EPDM? Maybe he will get a few more years, maybe another 20. Who's to say. A complete rebuild with new boiler, controls and HX seperation would cost tens of thousands. And the Solaroll is still the weak, and unknown, link.

Ya never know what you may find out there. A small body shop in my home town has a actual garden hose radiant system, with over 10 years on it, imagine that

Meanwhile I have a customer that has been waiting almost 3 friggin weeks for a Weil CG-4 HX that crapped out in under a years time. So much for "holding company" boiler manufactures and their incompentant reps.

hot rod



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