SFS led is on on a master temp 400b

[pilleway]

Hi, in the past weeks I have experience a problem with the equipment, the issue is that starts fine and after a minute or so it shuts off.
t trouble shut the problem, following the flow chart and according to it everithing is ok, but today I found out that it is reaching exhaust temperature of more than 480, SFS sensor resistance is ok, thermal regulator is new and propely seated, fuel presure and volumen supply is correct, no error codes at all, but today I found out to day the exhaust gas temperature (high) is causing to shut it down and service heater light will stay on.
How come the temperature will increase from a combustion poin of view? In a LP application will a richer mixure will cool down the exhaust gas temperature? (As it does in a combustin fuel engine) or it does it different?

Any help or recomendation will be appreciated!
regards to all!

 

[JamesW]

It might be a scaled exchanger. The 400 hd is slightly less efficient than the regular 400 model. So, the exhaust is already hotter.

If the exchanger is scaled, there is less heat transfer and therefore the exhaust will be hotter than it should be.

 

[pilleway]

James, thanks for your comment, I will verify if it is scaled!

 

[pilleway]

How will I scale out the excanger? Disasemblingit and rubing it with a wire brush? or a pruduct?
how can I prevent in the future to build up again?
Thanks

 

[JamesW]

The high exhaust temperature might be due to low water flow, a sooted exchanger or a scaled exchanger.

Check water flow, check the internal bypass and any external bypass. Check pump speed (if variable speed) and make sure that the filter is clean.

Check for a sooted or scaled exchanger and clean as needed.

Here's a video about getting to the heat exchanger.

De-liming a Sta Rite Heater part 1.mpg - YouTube

Scaling happens when the CSI gets too high. Maintain the CSI at -0.3 to 0.0 to avoid scaling.

 

[pilleway]

James, I have seen the videos and it is somthing I can do, I will get o-rings and look for time to do it sine is at my father's house, and will be some hours work but will get solved, it is very reasonable in the master temp since it is about 7 years old.
once again, thanks for the recomendation and guidance!
hava a nice weekend
Miguel

 

[JamesW]

You can try circulating a descaler product through the exchanger.

Remove the thermal regulator so that it doesn't block flow.

Ask the Pool Guy: 10 Steps to Descaling A Pentair Pool Heater - YouTube

There are descaling solutions available. I would avoid hydrochloric acid (muriatic acid) as it can damage copper. It can work at lower concentrations, but I would try a less corrosive mix first.

You can use distilled white vinegar for the descaling solution.