Hello, I recently purchased a 3,500 sq ft single-level home on a concrete slab with a 3 car garage. The only heat source is radiant heat pex tubing in the concrete. There are 3 zones in the house, 1 for the garage and 1 for a water storage tank to heat the hot water for faucets, showers etc.). The system is powered by a Weil-Mclain gas boiler and a Weil-Mclain Gold Plus 30 water tank. When I bought the house I noticed the 3 thermostats in the house were all set to 60 degrees and the garage was set to 40. The actual temp. in the house was staying around 70 and 55 in the garage on cold days. After being here a week, I decided 70 feels plenty warm and I tried turning the thermostats down to 50 (left garage at 40) to see how the comfort level would be. What I am noticing is that the house is not getting any cooler, it's still 70 degrees average. In the utility room the control panel has lights for each zone, the water storage zone (zone 1 priority) is the only zone that ever seems to be running, but the floors in the house are all staying very warm. Does anybody have any experience with these systems? I turned my thermostats all the way down (so they won't ever trigger the zones) and the house is still staying very warm and the boiler runs often -- It seems I have no control. I can provide pictures of the setup and more specifics if it helps! Thank you....

What climate zone are you in?

It can take many hours for the slab to cool down after shutting of a hydronic radiant floor heating system. However, if the boiler is dedicated to the heating system and it is still cycling, you are correct that something is not right with the controller. A proper controller for this type of heating system should have both indoor and outdoor temp sensors, and slab temp sensors. A better controller would have internet access and use weather forecast info in it's algorithm. Just using an indoor temp themostat is a bad way to control this heating system. You should probably hire someone knowledgable about these systems to visit your home and sort out the issue.

You have to provide a few more clues,
Is the boiler condensing or non condensing? if you are not sure what is the Weil-Mclain gas boiler model the good folks on this blog can tell you then,
If it is a condensing unit it may have out door reset built in, but not applied.
Next what is the delivered temperature to the slab heat areas? Perhaps the installer did not understand what they were working with, you may be dumping 135 degree water in to the slab, hard to tell from here.
If it is a non condensing boiler is there a primary and secondary loop and a way to mix temperature down?
How are the pumps controlled Taco box, Tekmar??
Details will provide the clues
Dan

if you turn a thermostat way up, should see:

1. a relay box should show the heat demand
2. either a zone valve or loop actuator should open, or a zone pump should run
3. a heat demand should be placed on the boiler. if it has its own pump, that should run, and if your water temp is low enough the boiler should fire. that assumes there are controls... otherwise it should just fire up to a high limit.

those are the basic steps. so turn up a thermostat and see if you find out if those things are happening, and then turn the zone back down and see if you can see them stop happening. If not, you can at least see WHAT is not happening.

pictures are good too.

Here is a link to some pictures of the boiler room -- there is also a picture of the closet on the other end of the house. CLICK HERE

I am in climate zone 4 (WI).

It appears to be a Weil-Mclain Gold GV boiler installed in late 1997, which I think is condensing?. All water valves in the room are fully opened. There are no floor sensors or outside sensor

I could not find a model number on the 120V pumps.

The control board is a ARGO ARM866DP. There are spots for 6 zones, 5 are being used. The first zone is labeled priority. When the water tank thermostat calls for hot water the light for the Priority zone lights and the boiler fires up. The remaining 4 zones are the 3 zones in the house and 1 in the garage. IF I turn up any of the thermostats in the house past current room temp it will kick on the designated zone light and the water heater will fire up.

When I inspected the house at the beginning of November the thermostat on the water storage tank was damaged and disconnected so the priority zone was never on and there was no domestic hot water unless we jumped the wires that get connected to the thermostat on the tank. I would notice the lights for the other 4 zones on and the house thermostats were set at 62 degrees (Actual room temp was getting about 70ish), gararge thermostat was disconnected so that zone would not run.

When I bought the house 2 weeks ago I immediately replaced the thermostat on the water storage tank -- since then the house has been very warm since the water storage tank calls for heat a lot, and the boiler seems to run a lot, despite all of zone lights (except priority zone) never coming on.

I realize I will likely need to get a radiant guy on-site to take a look, but I'm mostly interested in learning how this system is supposed to work since I'm going to be living here for awhile!

Let me know if there are other questions or more pictures that are needed to help me figure this thing out!

Thanks so much....

Not condensing, low efficiency at 87%...almost a high efficiency boiler but still cast iron.

http://www.cpsc.gov/cpscpub/prerel/prhtml98/98107.html

Control is the thing. A call for DHW not satisfied with bypass to the heating zones. Try to find a smart guy.

well, sounds like you might have messed up your thermostat replacement. but that SHOULDN'T heat your home unless you have ghost flows through your zones.

does it STOP heating everything if you turn down your DHW thermostat? how about if you turn it off/disconnect it completely?

I've looked at the pics and it seems as though the pumps are pumping upwards to the same horizontal header. It is far better to pump into the floor loops than draw from them. Also, the mix valves are on the suction side of the pumps and the pump does not pump into the floor or through the proper port of the mix valve. This piping is so over complicated for the job, I think it needs to be redone.