Radiant Heat Questions.

Norm Harvey

Chris,

The best way to start is to do a heat loss calculation on the building, then take your radiant tubing size, installation method, spacing, and loop lengths and determine mathematicly what temperature you need to heat the space.


Piping arrangement plays a big rome in controlling the temperature going to your radiant. Can you tell us more or show us some pictures of the piping? My gut feeling is that your temperature going to the radiant may be too high.

What do you have to control the radiant? An out door reset control, a circulator relay, or something else? Also what kind of feed back do you have if any? Floor sensors?


It sounds like you could be well served by a radiant heating professional.

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Chris_107

Radiant Heat Questions

We have an oil-fired, hot water boiler that supports a radiant heat system in the house. One zone supports the main house where the radiant heat pipes are in the ceiling of the rooms. The second zone supports a heated, glassed in, insulated sun room, where the pipes are in a concrete and flagstone floor. There is 1 foot of fiberglass insulation in the attic over the heated ceiling. The boiler aquastat kicks in at 140 deg F, and off at 160 deg F. There is also a hot water heater that runs off of the boiler water.

Can someone answer some questions, please?

1. What temperature water should be flowing through the radiant heating pipes? When we first got the house, an inexperienced service guy who was cleaning the boiler turned up the water temperature in the house to 150 deg F, and cracked all the ceilings. Now, we run 110 deg F water through the house, and 120 deg water through the sun room. Is this correct? Wall thermostats are usually set on 70 deg F.

2. The water temperature flowing through the system is controlled in two ways. There's some sort of an automatic valve that controls the hot water that gets mixed in with the colder water coming back from the house. There's also a valve that controls that flow of cooled water coming back from the house. The instructions on the tag tell us to control the temperature of the house water by adjusting this cooler water valve. On the sunroom circuit, there's no automatic valve. Just a manual valve controlling the injected hot water, and another one controlling the cooled water returning from the sunroom.

Why are there two valves, and which one do we use to control temperature? Right now for the sunroom circuit, the return cooled water valve is wide open, and we're using the hot water valve to control outgoing temperature going out to the floor.

Thanks
Chris

Chris_107

The system was built in 1950, so there's no feedback, technology or any control beyond a thermostat. Since the pipes are buried, and there's no documentation, I have no idea about pipe layout, area, or anything beyond the fact that the piping is 1/2 inch, HD copper tubing.

Is the idea that the circulators should run 24 / 7 pushing lukewarm water for long periods of time, or should warmer water be used so that more heat is pushed faster to the rooms, but for short periods?

Do you know of any good books written on the subject?

Thanks for taking the time.

Chris

Gordy

Radiant ceilings

I have Radiant ceilings in my house from the 50's.

My ceiling piping is 3/8" copper tubing embedded in the plaster. You can purchase a 50 dollar IR thermometer to trace the piping layout if you wish.


Sounds like there is a manual sort of mixing system that uses valves rather than a mixing valve that is designed to do this. Maybe they were tampered with from the original settings.

My boiler is set at 160* but after going through the mixing valve the system sees 115* supply water.

According to my original Chase Copper, and brass Literature you could go to 150* with out damage to the plaster. Though that is rarley needed.


Some information to share would be if this is original boiler and near boiler piping. Pics are worth 1000 words also.

I have toyed with continuous circulation verses bang bang circulation.

With the simple Tstat setup you have, constant circulation will make you over shoot your room setting because you are purging the hot water out of the boiler after the Tstat is satisfied, and the boiler shuts down.

Plus the fact your burning electricity to run the circ. which is probably a 200 watt B&G 100 or HV.

Gordy