Burping a Raypak Boiler

[JGinther]

We just bought 3 junk car washes from a bank and are working on fixing them up. One problem I am having at one location is with a 1.1 million btu Raypak boiler which has the pump and flow switch mounted directly on the header (Raypak factory design). It is used for hot water, and is recirculated through an open gravity tank. The problem I am having is that the flow switch wiggles and won't maintain a good contact on the microswitch. I have replaced the spring on the flowswitch to a very light duty type that barely returns the switch to open when the pump is off. I think the problem is that there is air trapped within the header, making flow around the pump impeller intermittent and slow. I think its stuck there because the inlet and outlet piping go down lower than the heat exchanger before going back up to the tank. Rerouting the plumbing is next to impossible due to the layout of other equipment. Does anyone know of a trick to burp the boiler? I have tried loosening the header and pump bolts, but I just get wet - nothing fixed.

 

[mjwalsh]

We just bought 3 junk car washes from a bank and are working on fixing them up. One problem I am having at one location is with a 1.1 million btu Raypak boiler which has the pump and flow switch mounted directly on the header (Raypak factory design). It is used for hot water, and is recirculated through an open gravity tank. The problem I am having is that the flow switch wiggles and won't maintain a good contact on the microswitch. I have replaced the spring on the flowswitch to a very light duty type that barely returns the switch to open when the pump is off. I think the problem is that there is air trapped within the header, making flow around the pump impeller intermittent and slow. I think its stuck there because the inlet and outlet piping go down lower than the heat exchanger before going back up to the tank. Rerouting the plumbing is next to impossible due to the layout of other equipment. Does anyone know of a trick to burp the boiler? I have tried loosening the header and pump bolts, but I just get wet - nothing fixed.

JGinther,

We had the paddle actually break off on a McDonnell Miller flow switch. It was very bad scenario because the broken lower part pf the paddle had to be found within the piping ... in who knows where spot. It might have been because the extra flow velocity that a mechanical engineer said we needed. By repairing the flow switch using more than one paddle ... it reinforced the pivot part where it can break off. That was over 15 years ago so it worked for us. Did you check for a weakness or a hair line crack in the part of the paddle where it actually pivots?

At strategic points in our piping we have Gerand Ball valves where we can check the actual flows with a Gerand Meter ... so we are not in the dark about when there a potential flow problem. We utilize some condensing boilers that are more vulnerable within their internal combustion chambers to low flow ... so specific minimum flow is more critical.

As far as air ... the large back screw on the Grundfos Pump is really great for rectifying that. We also use air perjures in strategic places in the piping.

Hopefully, this information based on actual experience has been explained in a way ... you & others can understand ... & potentially helps.

Mike Walsh www.kingkoin.com

 

[JGinther]

Thanks Mike... The flow switch has a double stainless long paddle of about 5.5". It almost touches the back part of the header. There is no physical problem with the switch as far as I can tell... Just a flow problem. I really really wish I could find such a bleed port on this set-up, but it is OEM Raypak design (but the piping is obviously not). If you hold the flow switch with your finger, you can feel lots of pulses pushing the flow switch, which is what makes me pretty sure there is air trapped in the heat exchanger and making the pump have intermittent flow pulses. It does this regardless of if the flame is on or not. I'm almost considering tapping the million dollar header and installing a bleeder...

View attachment 597

 

[cantbreak80]

I doubt it's an air pocket...those pumps move a lot of water. Maybe it's an eroded impeller...no so unusual with those Raypaks.

You might also try straightening the flow switch.

I once found a titration bottle stuck in the volute. It had fall into the open tank and got sucked into the boiler supply. I'd wondered where that bottle went for over 5 years.

 

[2Biz]

You could "Temporarily" bypass the flow switch to eliminate it as being the problem.

 

[JGinther]

Thanks for the input... i have pulled the pump and the flow switch numerous times. The pump is in great shape, as the previous owner never used the boiler. I know that flow is an issue because the outflow water will get very hot fast. The water boiles and pops if the switch is pushed in... I am 99.9% sure air is stuck, which is causing the pump to not push enough water (air entrainment around impeller). I did not however, see a titration bottle. I will look for that...

 

[cantbreak80]

How about sticking a garden hose into the boiler supply fitting in the tank and turning the water on full blast?

 

[soapy]

You might try calling Huron valley supply. They have a lot of experience with raypak systems.

 

[cwguy.com]

How about sticking a garden hose into the boiler supply fitting in the tank and turning the water on full blast?

Since the boiler was not used.... are the pipes clean and not clogged? Their could be built up crap in the supply pipes? Maybe cleaning them out like cantbreak80 kind of suggested? You might not be getting good pressure? Or good flow to the boiler?

 

[MEP001]

How about sticking a garden hose into the boiler supply fitting in the tank and turning the water on full blast?

I was going to suggest the same thing. I've had to do it to a couple boilers to get them primed.

 

[JGinther]

Thanks again. I guess i should have wrote a book on all the things i tried first because i did all of those including calling huron valley (they dont sell the integrated pump ones). I think the hose thing would work if i had a 2" garden hose. I think i am just going to replumb the pipe going from the boiler back to the tank... The whole setup is stupid anyways... the holding tank is 13 gallons and the boiler is 1.1m btu... The original equipment company didn't have a clue, or didnt care about the gas bill and wanted to save a few bucks on the tank...
Thanks again for all the ideas!

 

[cwguy.com]

If you replumb I would use pex and rip out the copper. Pex is a lot easier to work with. I used copper rings not the clamps.... and only up to 1" though.

 

[slamdvw]

Check pump rotation direction? A backwards spinning pump will sometimes pump, but at a much lower rate.

 

[Stuart]

Is the pump above the water level? If so you will have a tough time getting the system filled and staying full if there may be a leak somewhere.
One way to attempt to fill it is as stated earlier is with a hose. Hook it up on the outlet side of the T&P relief valve. Turn water on, manually open T&P valve. While the water is on turn the circ pump on. The combination of these may be able to get things started.
Hope this helps
Do you have a picture of the water supply side of the boiler?

 

[wash4me]

You can use a swimming pool pump to get high flow. Also you can get a separate flow switch mounted in the piping to the boiler and just wire into that one. Also might help to put an expansion tank with a bladder and charge it to 10-15 psi........you could use a hot waterexpansion tank but it's not technically big enough. I'm wondering if the piping is designed to have sufficient flow to properly open the flow switch. Can you plumb in a near boiler bypass to get more flow?