Radiant Floor warm with thermostat off ?

Unknown

Hmm.. The tekmar should have an outdoor sensor. If so, it will shut itself down when it's warm enough outside. This is called "warm weather shutdown" or WWSD.

However, you just made me nervous. Having the water sitting in the tubing all summer is not a problem... UNLESS this is an open system (that is, the water in the pipes is your drinking water). If that's the case, you need to get a heat exchanger in there, that's a potentially dangerous set up!

If it's not an open system, the tekmar will exercise your zone valve through the summer so it doesn't stick, even when it's in WWSD. And the water sitting in the pipes is no problem.

Rodney Summers

Hi,
I recently purchased a home that has a 3 zone boiler. Two zones are for baseboard heat/hot water and the 3rd is for an addition that was put on the house which contains radiant floor heating.

I was told by the previous owner to turn the radiant zone feed valve off in the summer months, so the room doesn't get warm. I did this over the summer and that was effective. I recently turned the valve back on and noticed the floor gets pretty warm considering the thermostat is not calling for heat as it is off. Is this normal for a radiant floor system? The only controls I noticed on the zone beside the radiant heat manifold was a few shut off valves, the circulator and a Tekmar controller (I am assuming for temp control). Can someone shed some light for me here?
Thanks in advance!
Ron

Terry

scheme

a piping scheme would help addressing this issue.

sounds like ghost flow and/or inadequate mixing method.

post a sketch of how this is piped and I'm sure one of us "wallies" will be able to shed some light on the matter.



EIN

Rodney Summers

Ok...after reading some more about the TekMar 352 Control, I am thinking that may need to be looked at. I did not notice a mix valve on that zone, so I am not sure if it is needed with this setup. Here is a link to my controller:

http://www.tekmarcontrols.com/acrobat/d352.pdf

bill clinton_3

If you have to "turn the radiant zone feed valve off in the summer months, so the room doesn't get warm" it would seem you have no positive shut off on that zone. If so, other zones operation are likely to cause "ghost flow". If that floor is above the boiler, thermosiphon could be occurring. I have siphoned a bunch of therms in my career, so I know its a phenomenon to respect. Solution in any case is to provide positive shut off when the t'stat is off. An appropriately placed zone valve works well.

Bill

Rodney Summers

That makes sense. I took a closer look last night and the TekMar control (352) has an electronic mixer valve connected to it (Honeywell F2-9643). The valve seems to open and close properly when I initiate a test on the Tekmar control as I can see the servo motor moving and hot water mixes into the zone.

My guess at this point is that I need to verify the settings on the Tekmar as it has a few different options (boiler temperature, heat curve, and unoccupied settings). It also has an outdoor sensor to compensate for colder weather in conjunction with the wall thermostat. There is also a circulator on there (Grundfos UP 15-42FR). I probably should verify that is working as well but wasn't sure how to check it. If anybody has any insight on that, let me know.
Thanks!
Ron


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Unknown

is the room overheating?

If not... you may have a constant circulation system. GREAT!

If so... then the ghost flow thing may be a culprit.

Rodney Summers

Hi,
It was overheating and I am not sure if it was due to the fact that I replaced the Tecmar Thermostat with a standard digital one. Since I put the Tecmar back, the room floor is only slighly warm as it was when we bought the house in the spring. Maybe there is something unique about that thermostat and it can't be replaced with just any standard one.

So I would say typical function of this system as we have experienced does make the floor slighly warm hence the reason for shutting it off in the summer. Whether this is normal for a radiant system of my type is still the question.
Thanks,
Ron


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Unknown

Huh, heating help thinks you are ken

I would guess you have a Tekmar RTU (not thermostat) in the room.. maybe an 054. That would give you constant circulation. What it's doing is sending info back to the Tekmar controller, telling it what the temperature is, so the tekmar can figure out how warm to make the floor... constantly.

Without the RTU, the system is "flying blind" and overheating the space because the controller wants to do constant circulation but does not have an RTU to assist. I believe you may be able to set the tekmar to non-constant circulation, and use a relay with your new thermostat to trigger the zone pump, but this is inferior to constant circulation so I would advise keeping the original RTU. Constant circulation w/indoor feedback is the cat's meow, use it and enjoy it!!

Rodney Summers

You are correct, it is an RTU (054), so that explains it. So now that it is back to operating normally, do I want to change a setting on the Tekmar Control for the summer, so the floor is not always warm? Or is the recommendation to shut the zone vlave off in the summer as the previous owner told me to do. It seems like that would be a bad idea to just have water sitting in the tubing all summer without opening/shutting the valve regularly.

Not sure how familiar you are with the TekMar control but I am not
Thanks for the help!
Ron

Rodney Summers

It does have the outdoor sensor and right now it is in WWSD mode. I tried cranking the heat up on the RTU and it starts to heat by opening the mixig valve. I don't think it is an open system because this is on a different zone than the drinking water but quite honestly I am not sure how to tell.

The info you provided was very helpful and much appreciated. I learned a lot this week and feel much better about what's down there. Does anyone have advice on how to tell if the circulator is working properly? When I turned up the heat, I didn't hear it making any noise unless they operate really quietly. As I mentioned it is a Grundfos UP 15-42FR Circulator.
Thanks!
Ron

Unknown

Glad to help!

You can tell if the pump is working, generally, by touching it. It's hot if it's running. Touch carefully . The other way to tell is... are you getting heat? if so, it's either pumping or you have a lovely gravity fed system that I wish I could design on purpose . also if you have a thermometer on the radiant side, you can see if it rises when the zone valve opens.

What is your heat source? That will help tell if you have an open system or not. Generally they are water heaters, without heat exchangers.

Rodney Summers

My heat source is a Trianco Newport Tankless furnace (oil). I am getting heat to my first level but my second level is not. I think there may be some air in the system as I had to replace a couple of valves. I'll try some purging tonight and see if that does it. The circulator for the zone that is not getting heat feels like it is running but isn't getting very hot.
Thanks,
Ron