Wall hung Lochinvar Nat Gas boiler Harmonic on ramp up 0-50%

guardian

We have a Lochinvar (Humming) on start up. system has been in for 6 years Nat gas. had this happen on prop gas fired.
1st time had this happen for nat gas. Checked gas valve for corrosion on venturi . unit serviced in june 2015
STILL ON HOLD WITH TECH SUPPORT. Day 2!!!!!!!. any suggestions? ( Can't beat the old cast iron and chimney )

Ironman

Set the throttle to allow the maximum Co2 allowed in the manual. Don't use a flex connector or CSST within 10' of the boiler. Make sure the burner, HX and collector are clean. Keep inlet gas pressure no higher than 7" on natural.

One or more of these should correct it

ced48

I've had problems with a WH55 running on propane for three seasons. I still have harmonic issues at certain low fire speeds. Adjusting the fuel mixture richer does help with the whine, not completly, but if you go to far, it makes for rough running at other speeds. I spent many hours on tuning, including the pressure differential valve, with the guys at Lochinvar, without much success. I also have tried many other things suggested by the members of this forum, none have seemed to help, or harm, overall performance.

If you solve this thing, please post your findings.

Steve Minnich

I have had this issue on propane fired units. I followed Ironman's advice on the combustion tuning and it solved the problem once and for all.

tim smith

Is this a WHN boiler? Some times just tweaking combustion #s will get the harmonic moan out of the firing.

ced48

I not sure of how guardian would describe the sound, but mine, and I have a hunch, his, is more of a whine, not a moan.

I also assume that he might be hearing the sound only on the modulation up, because his system doesn't modulate down below 50%, or he would hear it on the return down as well.

More details on guardian's problems might be of help-

HeatingQc

On the last one we got doing this, we've done all we can on combustion, nothing changed the noise. The client asked for a replacement unit. We changed it. Same issue. Finally, it was the arrangement of the LP line and regulator that caused the vibration.

hot_rod

I think the fuel quality and energy content of LP has, and is changing. Some units that have run fine for years need to be re adjusted to the changed calorific content fuel.
Regulator supply at loads and gas pipe size, of course need to be checked.

ced48

HeatingQc said:

On the last one we got doing this, we've done all we can on combustion, nothing changed the noise. The client asked for a replacement unit. We changed it. Same issue. Finally, it was the arrangement of the LP line and regulator that caused the vibration.

Can you give specifics on the regulator and gas line setup?

HeatingQc

null

I'll try to dig to see what it was. A small residential KBN106 was installed in a single home, but we didn't do the LP piping and regulator. I'll ask the Propane supplier and get back to you.

ced48

That would be great-