Raypak 406a Heater

[HalcyonDays]

I have a Raypak 400kbtu propane heater acting up. When I turn it on it calls for heat and the burner fires normally, after a few seconds, the flame goes out briefly then comes back on for a second or two. The heater continues in this fashion. No error code is given. I have replaced the gas valve, and have confirmed that I am getting 24V to the valve. I've taken the header off and confirmed that there is no calcification (good to know). Any thoughts on other causes? faulty HL switch? Faulty pressure switch?

Thanks for any help

 

[mgarf33]

Model #?

 

[HalcyonDays]

406a

 

[mgarf33]

Auto Ignition type?
The symptoms are consistent with a draft issue.
However, ignition failures typically result in a fault code, or lockout, whether it be a draft proving switch, flame sense, etc. The board seems to be resetting intermittently. So, you may want to look at it as well.
I would also check your manifold fuel pressure. You may be over fired, or not have venturi air adjuster set properly (if it has any).
Any possibility your getting air in the fuel lines?
Another strong possibility, check the seal behind the draft motor. It may be leaking, causing insufficient draft through the heat exchanger. The diagnostic codes may not display this as a draft pressure fault but will cause the flames to become erratic.
It's hard to say without more information. Have you gone through the step-by-step trouble shooting flow charts in the manual?

 

[ps0303]

Are you sure you have propane in your tank? If you do then your problem is either the ignitor or the control board although you should get the ignition lockout code on the display, that is if this had a digital display on it. You could also have a sooted up heat exchanger which will cause a similar symptom.

You should not have to ever change the incoming gas pressure unless your new gas valve is not the correct type. There is no draft motor on your model so that is not an issue.

 

[HalcyonDays]

Thanks for the feedback guys.

There are three identical heaters sitting next to this one all functioning properly and there 3000L of gas in the tank. Since my last post I have tried the following:

- Swapped pilot assembly with a working unit
- Swapped control board with a functioning unit
- Isolated the pressure switch, the HL1 and HL2 sensors by shorting the leads

I didn't mention in my previous post but the units are fitted with a power vent and are venting through the sidewall of the building. The power vent starts up just fine and is moving a normal amount of air at the exhaust.

Paul, how would I go about diagnosing a sooted up heat exchanger? That sounds like a logical next step.

Thanks again guys,

Adam

 

[ps0303]

Remove your power vent and then the top panel of the heater and then you can look down at the heat exchanger to see if it's all sooted or not. Is the power vent on this unit operating correctly?

 

[HalcyonDays]

The power vent is operating correctly and I've confirmed no obstructions in the stack. I just removed the power vent and checked the heat exchanger it does not seem to be overly sooted. I've attached a photo. I also tested the vacuum switch inside the power vent and it is functional.

To answer a previous post the heater is spark ignition. The flames cycle on and off a couple of times now then stay out completely. The display screen seems to think everything is operating correctly and the pilot is staying lit and power vent keeps blowing. These things throw an error code for just about anything so I can't figure why I'm not getting at lease a hint on this one.

Adam

 

[ps0303]

To me that heat exchanger looks plugged up thus not allowing the unit to fire correctly. Compare this unit to another operational one and see if they look different. I'm betting they do. If so, you need to clean the heat exchanger. Pretty simple to do.

Not sure it's not throwing a error code either.

 

[mgarf33]

You said that you replaced the gas valve. Are you certain it's the correct valve? Did it need to be converted to LP?

You may have a faulty main valve solenoid on the new gv.

It would not show up as a fault because the pilot assembly senses the flame.

Does the pilot drop out and ignition begin to tick again?

Or does the pilot remain lit and main burner only cut out?

Does the gv continue to receive 24v when the flames drop out?
If your sure it's set up for LP, then the new valve may be bad.

 

[HalcyonDays]

Paul,

I'll have a go at cleaning the heat exchanger. Can you give me some insight on the procedure?

Adam

 

[ps0303]

Take the top of the heater off all the way. Then remove the burner tray after shutting off gas and electric. While you have the tray out, look at the refractory to see if it is damaged. If it's flaking off, you need to replace that once everything is cleaned up. Once the tray is removed you can use a simple garden hose with a nozzle on it that produces a strong stream. Spray down from up top for a few minutes hitting the entire heat exchanger. Then I would set the top on and then spray up under the heat exchanger where the burner tray was. If that unit is as clogged as it appears, hopefully you will get it all out with the hose. No need for a pressure washer or anything rough like that. Hose it down from both sides a few times and see how it looks.

 

[HalcyonDays]

Thanks for all the help everyone. In the end the issue was the vacuum switch in the power vent. The switch was working just fine, but the hose running from the stack to the switch was cracked and leaking. Replaced and all is working fine. No error code because the power vent is an add-on that does not wire into the control board. Since I had it torn apart the heat exchanger got a thorough cleaning anyway.

Paul, I especially appreciate your help on this.

Adam

 

[ps0303]

Glad you found it.