RayPak High Limit Popping

[Rudy]

We have a 15 year old RayPak that "pops" the High Limit intermittently (Floor Heat Boiler). It seems this happens only when it gets really, really cold outside.

What could be causing this?

One of the remedies in the operating manual suggests changing the modulating valve setting. Help me here.......there's a bypass valve plumbed between the input and output of the boiler. It's presently about 15% open (presumably to cycle warm water back to the heat exchanger to lessen thermal shock????). Would I want to open, or close this bypass valve? How do you know how "much" to bypass back from the output to the input of this boiler?

Other ideas?

 

[dogwasher]

I'm not sure what your set up is like but for the floor there should be a mixing valve to allow cool return water back into the floor supply(this return line would be piped into the supply run before getting pulled into the pump) to regulate the floor temp at 120 degrees. You cannot allow the water entering the floor to get above 120 or you will damage the concrete/tubing in the floor. If your tripping the high limit that could be due to low water flo...could be closed valve or pump going bad?

 

[JIMT]

Rudy,
If the antifreeze is getting too hot then you should close the bypass valve some to lower the temperature. This valve allows some of the heated water to re-enter the heater which causes it to be heated again. If you close it too much then it might cause water to condense in the heater and cause it to rust.
JIMT

 

[6t7gto]

My Ray-pak did that.
First, the coil was sooted up. cleaned that.
Second, the temp setting on the gas valve would vibrate to the highest setting causing flame roll-out and trip the high limit.

david

 

[Rudy]

David you were right on!

I checked for soot, but there was none. The modulating setting on the gas valve, however, was set on the highest setting of "9".

I placed it on "2", and it has been running steady all morning. It was 7 degrees this morning...so it will take some time for the slab to warm up.

Vibration over time must cause it to change??????

 

[6t7gto]

My manual states these settings:
position
lo...110 Degrees
1....120
2....135
3....145
4....155
5....165
6....175
7....190
8....200
hi...210

I don't remember who on this board but he recommended a setting of 4 or 5.
Mine is a model 514.

I put a rubber band on the knob to stop it from vibrating to a higher setting. I don't know if the stem for the knob can be tightened to prevent changing settings.
david

 

[ScottV]

I also have a Rapac that is 5 years old. My modulating valve is set at 4 until it becomes severely cold out and I increase it to 6. My Heating and Cooling guy told me it would run more efficiently that way.

 

[Rudy]

I called Huron Valley today, and talked to their Tech rep.

He told me that they recommend a setting of 2 or 3. This adjustment determines the temperature at which the gas valve "modulates" down, or in other words.....throttles down the amount of heat going into the heat exchanger. This would occur as the slab gets warm and more or less enters into a "maintain" vs. an "obtain" situation. It is more efficient to "maintain" a given temperature with a smaller flame as compared to using an "on or off" situation using gas burner cycling at full throttle.

With a modulating gas valve, (if the slab is cold), the valve setting would have no effect since the situation would be calling for "full throttle". It would only come into play as the circulating water warms to the preset temperature.

Right????