Raypak flame rectification problem

FRENCHY

Been doing battle with a Raypak WH-330 NG atmospherically vented boiler that is being used for DHW only.  Have replaced 1.  Ignition Module  2.  Gas valve  3.  ignighter 

Module sparks, pilot lights, pilot proves, burner lights.....

Burner will stay lit for an intermittant period of time.  When cold start up, will usually run fine till loses call for heat.  When warm, burner drops out after a few seconds to a few minutes. 

I have bypassed all safety's to no avail.  Cleaned heat exchanger, checked for positive draft.  Inlet gas pressure is 8.16" W.C.  (no change when burner lit)  Manifold pressure is steady 3.55" W.C.

Seems must be a flame rectification issue.  I have tightened and checked all grounds.  Also suspect may be transformer?  No voltage change at gas valve when burner running or before it drops out though. 

Tired of throwing parts at it...  Any suggestions would be much appreciated.  Anyone run into similar situation?

Thanks in advance!

JStar

...

Does the ignition module require a separate flame sensor, or does the ignitor act as one? Are they both clean, and catching a good amount of flame? Did you change the ignitor cable? Check for proper ground going to the module. Did you also jump out your aquastat control on the DHW tank? Maybe a limit is acting funny on the tank or the boiler.

lchmb

curious

When the burners drop out does the ignitor start sparking again? Have you tried removing the pilot from the burner mounting bracket and cleaned where it mounts on? I dont do any natural gas (propane) but is there a maximum inlet pressure? 

FRENCHY

Answers

The ignitor acts as flame sensor.  Ignitor is new (one of the parts I replaced yesterday).  It is catching good flame.  Played with adjusting its posistion in pilot flame just to make sure.  The ignitor and cable are one unit, so cable was replaced with ignitor.  I cut off ground wire terminal and re-crimped on a new end.  Also added a second ground to boiler chassis.  I have the transformer directly powering the ignition module to eliminate any safety's and take aquastat out of the equation.

When the burner drops out, I lose burner and pilot.  The ignitor does start to spark again, but when running back through ignition sequence.  Not a situation where ignitor starts to spark again, and then burner drops out.  I have removed pilot bracket and reinstalled a few times, does not appear that am losing ground contact here.  Was going to add a ground wire directly to the pilot hood (or as close as I can) today and see if that makes a difference.  I have spoken to Raypak tech support numerous times and they did not mention any problem with the inlet pressure at 8.16" W.C.

lchmb

ground wire

I would add the ground wire as you planned and then to make sure I would add a system ground back to the electrical panel to rule that out. I have had one case where the house ground (electric panel to earth) had been cut causing a similiar problem.

FRENCHY

System ground

Thanks for the suggestion.  There IS NOT a 120V ground wire on this system.  It is in an older apt. bld. and they are just using the conduit as the ground.

tim smith

Raypak dropping out

Ground wire to burner from ignition module. If still persists, could easily be a bad igniter flame rod assembly that has a small hairline crack. I would go after the pilot assembly after installing ground. Good luck

Tim McElwain

No one has mentioned

nor have you checking the microamp output when the unit is running and watching to see what happens to microamps just before it goes out.



I would also run the ground wire back to the gas valve.



What are the following make and number?



Gas Valve?



Module?



Pilot?



Is this a dual rod or single rod pilot?



Have you hooked up your combustion analyzer to this in order to monitor what is happening combustion wise.



What is your draft on the unit? You mentioned a positive draft it actually should be a negative  draft of say -.01, -.02 or -.03.



It is never a good idea to keep changing parts as you may actually miss the problem in the process.



I assume you are using a pre determined step by step process of trouble shooting.



I also do not like the fact that there is not a third leg dedicated ground some of these modules need to see that ground or they do not function so well. If you give us a list of what parts were original and then what you changed to I may be able to help you out.

Poolman1

Raypak rectification

What ended up being the problem?

Tim McElwain

Frenchy never

got back to tell us. This is very typical here. People present problems answers are given and we never hear from them again.

M Lane

^^^ I'm guilty of that.

We get busy. I'll bet it was the ground.

FRENCHY

SOLUTION

We get busy....

And / or

The solution is embarrassing because you forgot the first rule.

#1.  KISS

If memory serves....

This boiler had two limits that are on the circuit board (small potentiometers).  Not easy to tell where they are really set.

The 'maintenance staff' had played with them before I was part of the job.

The high limit was set just above the low limit.  The boiler would fire, and almost instantly hit high limit and shut off.

Adjusted the limits and she ran just fine....

It's always the simple stuff that you overlook or assume that bites you in the butt!

Tim McElwain

Thanks Frenchy

you are a true gentleman. You are right we often miss the simple things as we go looking for the complex. Good catch!