I need Help on controlling a Weil-McClain cgi floor heat boiler...

[spf8298]

I have a Weil-McClain CG-5-SPDN boiler that heats my floors. The problem is I have no idea how to control the temperature on this boiler. Mother boiler does work well and keeps the floors warm. The previous owners left me little help in understanding this unit. I know that it does have a White-Rodgers SPDT Remote Bulb temperature controller that tells it when to cycle on and off, but I have no idea how to operate that thermostat. Does anyone have any experience with this thermostat or boiler that could chime in and offer me some assistance on how to set it? I know the boiler is old and is a gas hog, but I also think some tweaking on temperature could save me some on my gas bill. Plus, it would just be nice to understand this piece of equipment.

I've attached a few pics of the boiler and thermostat.

 

[cwguy.com]

The "thermostat" is how you set the temperature for the boiler. It appears it is set around 65 on 75 off?

 

[6t7gto]

I added a second remote bulb thermostat to my boiler. It senses the outdoor temp for it to turn on the boiler.
I think I have it set to come on at 35 degrees outdoor temp.

 

[spf8298]

The "thermostat" is how you set the temperature for the boiler. It appears it is set around 65 on 75 off?

Is it just a matter of playing with those temp settings until I get the desired result (no ice) on the floor? Or are there some more defined parameters for different region of the country that I should have it set at?

 

[spf8298]

I added a second remote bulb thermostat to my boiler. It senses the outdoor temp for it to turn on the boiler.
I think I have it set to come on at 35 degrees outdoor temp.

This bulb remote has the actual bulb placed out in self serve bay monitoring the temp of the bay, but the confusing thing is the dial on the thermostat is set to 65-75 for the boiler. I wonder if I need one thermostat for the antifreeze temp and one for the outside temp?

 

[2Biz]

In my opinion, I think controlling your boiler from the return glycol temps is more accurate and a better method. I purchased a cheap infrared gun off amazon ($20) so I could check and monitor different areas of each bay. This helped me set zone valves and make fine tune adjustments to the return glycol aquastat. If I remember correctly, I set the aquastat to keep the bays at an average of 36° to 40° surface temperature which is what you want. I also have a 15° differential set on the aquastat.

The final aquastat adjustment kicks the demand heater on at 55° and off at about 70° return glycol temp. This setting (for me) keeps the floors ice free. The heater heats the glycol to 105° and mixes as it returns into the main loop…Primary/secondary system. Glycol goes back out to the bays at an average of 90°. Keep in mind every system will be different based on all the different variables…Loop length, main trunk pump flow (GPM flow), etc…

The reason I like this method over a slab stat, is its more direct and takes an average of all zone glycol temps. Not just a single point in a single bay. The other neat thing about the way my system is controlled, it is self- regulated. Once set, I have never had to make adjustments to keep the bays ice free. No matter how cold it is outside…Tested down to -16°!

 

[Rudy]

I agree with 2Biz. My original system had a "slab stat" which was simply an "on/off" setup which sensed the slab temperature at only one point.

I added an "air stat". At 34 degrees, this stat starts my circulator....basically moving the glycol around the loops. The previous "slat stat" was moved to the return line of the loops. I simply zip tied the sensing bulb to the outside of the pipe, and covered it with insulation. This stat now controls the firing of the boiler. If I remember correctly, (on my system) a return temperature of about 75 degrees keeps my slab deiced.

This setup has worked much better than the old one stat system. Heat is injected into the circulating loops only when needed....and appears to provide a more uniform control.

 

[2Biz]

To add to Rudy's post: My "Air Stat" is the secondary output on the weepmiser. It kicks on at 32° and latches in a relay that handles all the various loads I have put on it! Controlling the floor heat is one of the loads.

 

[wash4me]

If you are using the same temperature of glycol when it's 30 and below zero you are wasting a lot of heat at the higher air temperatures. You could install 2 bypasses on the boiler with a solenoid valve that opened on another air stat if it's below 15 degrees or something.

 

[2Biz]

If you are using the same temperature of glycol when it's 30 and below zero you are wasting a lot of heat at the higher air temperatures. You could install 2 bypasses on the boiler with a solenoid valve that opened on another air stat if it's below 15 degrees or something.

I don't quite follow what you are saying? When its 30° my demand heater cycles on and off to keep the slab just above freezing. Meaning it only heats the glycol enough to maintain 35-40° slab surface temperature...The colder it gets, the longer the demand heater has to run to maintain that same slab temp...Its all controlled from the return glycol aquastat. Example: at 32° my demand heater may cycle 15 minutes on 15 minutes off...At 15°, it may cycle 18 minutes on 12 minutes off. At zero it may cycle 20 minutes on 10 minutes off....Its actually very similar to this...The colder it gets the longer the heater stays on to maintain that constant 35-40° slab surface temp. So I don't see how you could get any more efficient than that?