Need help - was holding temp but now it can't

Greginnd

Looking for some advice on what to try. I have an insulated garage with radiant floor heat and a thermolec boiler. The floor has three loops. I think the system was installed in 2006. I just purchased the property last spring.



In September I turned on the radiant floor heat system and set the thermostat to 50. As winter came on it held that temp perfectly. About a week ago I noticed the temperature was down to about 45. Thinking that a recent cold spell (near 0°F temps) was responsible I tried turning the max temp setting of the boiler up. It was set at 5 and was getting up to about 85°F at the boiler. I turned it up so the max temp was about 110°F.



I checked it after one day and the garage temp was still only 45 degrees. I can feel the circulator pump running. I turned the max temp setting up even higher (~150°F). We'll see. I can feel some spots on the floor feel warm.



The loop pipes feel hot as the enter the floor and are cold coming back up.



I guess I'm wondering what I should check with this unit before I call in for service. Is it possible the circulator pump is not working properly? Or could there be something else blocking the flow? The boiler seems to heat ok as the temp goes up and down as it cycles the boiler.



I've never used one of these systems before so I don't know what else to look for.



I should mention the pressure looks to be about 12 psi.



Thanks for your help!

Gordy

Couple of things

Do you know if insulation was installed under the concrete? And I mean like 2" of XPS?



If there was a recent cold snap, and there is not insulation it could take a period of time to stabilize temps.



Is the garage itself well insulated?



Is there frequent garage door opening?



The temp setting on the boiler sounds like it was a little low. Is there outdoor reset for that boiler? Outdoor reset when properly setup monitors outdoor temps, and adjusts the boiler water temp accordingly.

SWEI

Outdoor Reset

All of the currently available Thermolec boilers have onboard ORC.



Can't speak to the older stuff.

Greginnd

I don't think it's heat loss

Yes, there is XPS insulation under the concrete. The garage was insulated well. My contractor finished the insulation and drywall for me this summer. I am not living there and the garage door is never opened. FYI - the garage is being built into a winery.



I don't think there is an outdoor reset installed. At least I don't see the sensor on the outside of the house. There are two sets of wires running into the box. One I presume is to the thermostat. The other, I don't know. It is not connected to the terminals marked OT that should be for the outdoor sensor. They are connected to a 4-terminal connection right next to each other.



I think the boiler is cycling fine. I wonder if there is a problem with the flow. Is there any way to check that? And is 12 psi too low pressure for the system or doesn't that matter?



Thanks.

Gordy

Check delta t

Of loops. See what they are. Got some pics would help also of boiler ,and piping.



If there is a large delta t between supply, and return of individual loops could be not enough flow. This should be checked when system has stabilized, and room is around set point.p

Greginnd

Pictures

Here are some pictures. The loops are quite warm going into the floor and pretty cold coming back out of the floor. I turned the max temp setting all the way up. The thermostat was set at 55 and after 24 hours it was still struggling to maintain 51 degrees. As I mentioned, something seems to have changed in the last couple weeks. Before the thermostat was set at 50 and the temp was maintained at 50.

SWEI

thermostat

tells you air temperature.  What is the supply water temp coming out of the boiler?



How hard is your water?  Scale can drastically reduce the capacity of the boiler's heat exchanger (and shorten its life.)

Greginnd

Thanks.

The boiler temp is now cycling between a low of 120 and high of 185.



I can feel the heat rise and fall on the pipe going to the pump as the boiler cycles.



A few weeks ago it was cycling between 80 and 110 and maintaining the garage at 50 degrees just fine.



I don't know how hard the water is but the system is filled with a propylene glycol solution and I presume it has been sealed since it was installed in 2006?

Greginnd

I really want to know

what I should be looking at before calling someone in. Is the problem most likely the pump (flow)? A problem with the boiler unit? or something else?



I have another question - why would there be two sets of thermostat wires coming out of the unit? I know one is attached to the thermostat. The second set of wires is not connected to the OT (outside temperature reset). I don't have any idea what these connections are. Here's a picture of where they are connected.

SWEI

Thermolec wiring

C & W1 connect to thermostat or end switch.

P & P connect to pump.

OT & OT to outside air temp sensor.



How can this boiler be varying its temp if the OAT is not connected?  You probably need to call a pro.  Where are you located?

Greginnd

Thermolec wiring

Without the OT sensor the boiler just regulates its temp based on the thermostat air temp (on or off) and the min/max temperature control setting. I have the min/max turned all the way up to 10 at the moment (min 118, max 190) and the boiler seems to be maintaining that ok as it cycles.



I just looked at the manual for this unit and see that the S1/S2 connectors are for a Load Management Control. I wonder if that has kicked in somehow and the system is being shut down in the evening? I'm usually not out here in the evenings so I don't know if the system is getting colder at night. I'm usually there in the afternoon.



I'm located in north Dakota near Fargo.

SWEI

S1 & S2

Are for the Dual-Energy mode.  Are you using this?

Greginnd

According to the thermolec manual

S1 and S2 are for Load Management Control. I don't think this should be a dual energy system. The house has a LPG furnace. That is separate from the garage which only has this radiant heat system. So, as far as I know, there should not be any dual energy switching for the garage heat.

SWEI

Is something wired to S1/S2?

Does your boiler have a mode select switch?

Greginnd

No

I don't have a mode select switch.



The wires connected to the S1/S2 terminals go into the wall and from there I have no idea.

SWEI

not sure what

S1/S2 will do on a boiler without the Dual-Energy option.  Quite likely nothing, but you'd better give Thermolec a call to be sure.  Electric baseload rates are not common in this part of the world and I've never used those terminals.



If the OAT is not connected, the temp dial regulates output temperature.  If that's varying, the return temp could be maxing out the boiler when outdoor temp drops and demand increases.  That could be caused by HX fouling.



The OAT was provided with the boiler and really should be installed for maximum comfort and efficiency.

Greginnd

Much appreciated

Thanks. I really appreciate your help and insight.



I have just heard back from the original owner. He says the boiler was set up to run on off-peak electricity regulated by the power company. So that's what the load control wires are for.



He thinks my pressure may be too low. It should be 15 psi and it is down to about 12 psi. That may be affecting the flow rate. I'll have someone come out and top it up with more glycol and see if that solves the problem.

SWEI

pressure & glycol

Are not going to help with the lack of heat.  12 PSI is plenty for a single story building.  Anyone adding glycol needs to test first, then replace and/or add as needed.



Is there a secondary heat source?  If not, the PoCo switch could be causing all of this, and explains the use of glycol.  You could easily install a manual override if you need heat during a peak period, but remember that it's going to take hours to recover from a long setback.  The strategy may have been to heat the building up enough during the night that the thermal mass took it through to the next evening when rates drop.  This would also explain the lack of ORC.   You need to set the space thermostat and water temp high enough to carry the load through the peak period.  185F is WAY too hot for a slab.  Crank the thermostat all the way up and start adjusting the aquastat until you get the desired afternoon/evening temp.  I'd probably start around 120F.  Once that temp is reached, you _might_ be able to turn on the ORC, but it has such limited control over the curve that I wouldn't count on much.  After you've done all of this, you can set the space thermostat to shut off the boiler in the event you fire a wood stove or other heat source in the space during off peak hours.

Fortunat

flow

From your description of a hot supply pipe and cld return, it sounds like you may have insufficient flow. In the second photo you posted I can see some flow meters on the loop manifold. Can you read them while the pump is on? What are your flow rates?



that will tell you if you have reasonable flow through each loop.



~fortunat

Fortunat

flow

From your description of a hot supply pipe and cld return, it sounds like you may have insufficient flow. In the second photo you posted I can see some flow meters on the loop manifold. Can you read them while the pump is on? What are your flow rates?



that will tell you if you have reasonable flow through each loop.



~fortunat

Fortunat

flow

From your description of a hot supply pipe and cld return, it sounds like you may have insufficient flow. In the second photo you posted I can see some flow meters on the loop manifold. Can you read them while the pump is on? What are your flow rates?



that will tell you if you have reasonable flow through each loop.



~fortunat

Fortunat

flow

From your description of a hot supply pipe and cld return, it sounds like you may have insufficient flow. In the second photo you posted I can see some flow meters on the loop manifold. Can you read them while the pump is on? What are your flow rates?



that will tell you if you have reasonable flow through each loop.



~fortunat

Fortunat

flow

duplicate post...sorry....slow internet connection and impatient operator.



~fortunat

Greginnd

No

There is no secondary heat source. Glycol was used in the system because this is a garage and may not always be heated. I don't think the power company is responsible because the power is not going off during the day.



I think there is an issue with the flow rate which could be the boiler getting fouled or the pump not operating properly. I'm going to call the company who installed the system to come out and look at it for me.

SWEI

just to make sure

Short the S1/S2 terminals and see if anything changes with the water temp over the next day or so.  If you're not getting a peak/off peak signal from the meter, you would do well to install the OAT sensor.

Greginnd

It was bad relays

Thanks everyone for your help and insight.



My heating guy took a look at the system. It turns out there was a bad relay that was not powering up one of the elements. Looks like it is working now that it has been replaced. He also disconnected the power company control wires.