More floor heat help

[slash007]

I am trying to get the floor heat going at my new site, but can't get the flow switch to work properly. I've tried every size paddle with no luck. If I open the bypass, it gets enough flow and the contact makes, but I can't leave it that way since the bypass is supposed to be closed. Circ pump is running, so that's not the issue. What am I missing? Here is how it looks:

 

[mjwalsh]

slash007,

There are non invasive ways for some HVAC people to check to see if the pump's impeller is still capable of its original flow or if the pump to motor flex coupler is properly engaging 100%.

We don't regret putting in Gerand Flow ball valves (with test ports) everywhere at our facility that the flow is extra pertinent. Opening the bypass does normally increase the flow ... which in turn would make the flow switch turn on.

 

[Toms PTcarwash]

That is a fin tube boiler. It is possible that the tubes need cleaned. Pop the fill plug off the expansion tank and look in to see if you have any flow with the pump running.

 

[GoBuckeyes]

That by-pass shouldn't be closed 100%. Open it about a third to half-way open and you'll probably be good.

 

[slash007]

That by-pass shouldn't be closed 100%. Open it about a third to half-way open and you'll probably be good.

I actually tried that, but flow switch only activates if it's 100% open. I looked at my other site and it was about 1/3 open, so I tried it.

 

[cantbreak80]

The by-pass valve’s purpose is to reduce condensation of the tube bundle (heat exchanger). On cold startups it takes a long time for the returning fluid to bring the tube bundle up to non-condensing temperatures. Condensation combines with combustion gasses and soot and drips from the tube bundle onto the burner tray and cabinet. This creates an acidic solution and will corrode the steel components of the boiler and the vent piping. Therefore, the by-pass valve should be cracked open about 30-40%...never fully open.

Low flow through the boiler will likely be due to an eroded pump impeller. The TACO pump is likely fitted with a ferrous impeller that will deteriorate over time…especially if the system has non-oxygen barrier tubing.

If your system manifolds have working ball valves, try closing them one at a time until the flow switch closes and the burner fires. This might verify the impeller failure.

Additionally, it appears that the system is filled with ethylene glycol (automotive antifreeze). All glycols are heavier than water viscosity…strong dilutions are harder to pump. Test the fluid with a refractometer. If the glycol tests under -15°F you might consider reducing the dilution.

 

[slash007]

Hmm, the fluid does look to be a very bright green, I wonder if they had been putting in pure glycol or 50/50. Pump impeller could also be worn I guess. Just throws me off that they say it worked fine last winter. I would have expected it to at least work for a week or two if it was the impeller.

Another question.. there are 2 thermostats on the wall for the boiler. The top one is labeled "on" and set to around 90 degrees. The lower one in the photo is labeled "off" and set to around 40. I only have one stat at my other sites. How do the 2 stats function, and what should I set them at?

 

[GoBuckeyes]

The 40 degree one is probably the air stat. When temp falls below 40 the pump kicks on.

The other one must control the flame. Where does it go to? We monitor the returning fluid temp and shoot for 65. Other people use a slab stat although 90 degrees seems WAY too high.

You need to see where they are wired into.

Actually I just looked at your pic again. Maybe the 90 degree thermostat is taped to the piping and monitoring the fluid temp to control the burner. Ninety is pretty high, but maybe they have the sensor after the by-pass. If so, you should move it before the by-pass as close to where it comes out of the slab as possible.

 

[mjwalsh]

Those old style aquastats & thermostats tend to not have the ability to "tweak" the turn off point & the turn on point (differential). That is why we replaced most of those that we had with more modern temperature digital controls.

 

[Roz]

You want floor heat to turn on in advance of reaching freezing temp in the bays so 40 is where we set our locations. 90 is your boiler temp as mentioned above, however you can fine tune the boiler temp so you do not burn more oil or gas than necessary with a temp gun from home depot. Check the outgoing temp on each line as you can vary them by the flow (assuming that you have ball valves on each line), and then check the return line temp. This will give you a sense of the heat loss HOWEVER you want to make at least one measurement with the outside temp at or below 32. We do not cut the boiler temp too close to the threshold as the heat the boiler throws off inside the office keeps the office a nice temp. A temp gun is also helpful to detect any issue with the boiler before a bad outcome reveals the issue at the worst possible moment.

 

[OurTown]

Ours has two stats. One is a slab stat that has the bulb in the concrete and normally set between 36-40F but sometimes as high as 50 if it is windy, colder and overcast. The second one is an air stat override and it is set at 15F and makes the boiler run all the time. To me it seems like a strange setup but that is how it was built (by Super Wash) and seems to work well most of the time.

 

[Waxman]

I had a situation where it seemed like my circulator pump was running but the boiler would not fire. I couldn't tell at the time because I didn't know what to look for, but the rubber coupling between the pump and the motor had failed. So the pump was not working but the motor was coming on… Just a thought.

 

[slash007]

Thanks for all the advice. I messed with it this morning and got the flow switch to kick on when the pump was running. I ended up putting a longer paddle on the flow switch and that, combined with a partially open bypass made it work. I did try a longer paddle initially, but had not opened the bypass any at the time. I also diluted the glycol some.

Anyhow, now on to the next possible issue. It seems my stats are backward. I don't mind if they work, but my circ pump seems to keep cutting on and off whether the stat is telling the boiler to fire or not. I'm wondering if it's overheating and shutting off, or if it's because I'm testing it with the temp outside at 65 degrees?

For my stats, the top one is labeled "on" and has the temp probe running to the outside. The bottom stat is labeled "off" and has the temp probe running to the return line. It's the pipe to the left of the bypass in the photo. The pipe covered in duct tape all the way to the left. The probe is closer to the wall, right before the nipple that is pointing to the ceiling.

If the bottom stat is below the outside ambient temperature, it will kick the boiler on as long as the top stat is set to a temp warmer than the glycol temp. Seems to be backwards, but that's the only way it works. The circ pump kicks one regardless of the stat settings as long as the switch on the boiler is on, but just keep cycling on and off. Any way that's normal?

 

[DakotaHoskins]

Those plastic love joys are also bad about wearing on those pumps. We have had one start slipping before it completely melted itself apart last year.

 

[slash007]

My circ pump runs for a few minutes then shuts off. If I leave it, it will turn back on again after 30 minutes to an hour then run and shut off like before. Here is a video of how it sounds. Anything particular I can look for as the culprit?
View attachment 20221018_153444.mp4

 

[GoBuckeyes]

Have you turned it by hand to feel for any binding? When it shuts off have you checked to see if you still have power to the motor? If so, that motor is thermally protected and it's getting too hot for some reason.

 

[OurTown]

My circ pump runs for a few minutes then shuts off. If I leave it, it will turn back on again after 30 minutes to an hour then run and shut off like before. Here is a video of how it sounds. Anything particular I can look for as the culprit?
View attachment 7193

It sounds loud to me. What does the coupler look like? I wonder when was the last time someone put oil in the oiler holes.

 

[Eric H]

I agree with both posts above. Probably needs some oil and the thermal overload is probably tripping.
You may want to wire in a 120v pilot light so that you know when the boiler is sending power to the pump. I used to have that same pump and it isn’t silent but is much quieter than yours.

 

[slash007]

It does turn easily when I do it by hand, so no issues there. I have another one on my hot water boiler and it sounds quieter for sure, but it's a different brand. This one is louder and has a certain noise that seems off to me. You can't really hear that in the video, but it isn't smooth. Never knew I needed to oil it. What kind of oil and where do I put it? Thanks!

 

[Eric H]

What kind of oil and where do I put it? Thanks!

I just use the same CAT oil that I use for the CAT pumps. It’s convenient and I already have it on hand. Just up I few drops in once a year before the heating season