Adding a two stage gas valve

DAS

Anyone have any pros or cons (warnings?) to us adding a Honeywell two stage gas valve for low and high fire settings to our EGH 85 Weil-Mclain?

Tim McElwain

What do you have

for a gas valve now? You will need two stage controls when you do this are you aware of that? Do you have a combustion air blower?



I would contact Weil-McLain as to the feasibility of doing that.



It would be best if done by a professional, are you a pro? There should also be a combustion test done and also a burner turn down test.



You may find that after you do all of this your comfort level when firing only on low fire may be affected. That is were the pro comes in who can advise you based on your existing radiation system.

DAS

Adding a two stage gas valve continued

Yes, there is a pro who will handle installation and over site.



Currently, there's the standard Weil-Mclain electric ignitor and the standard install that occurred 10 years ago - no combustion air blower.



I forgot to include the Honeywell low range vapor stat as well as a new relay.



Will do on the combustion and burner turn down tests. Thanks!



Anything else I need to think about?



das

terry ritter

Repost on Strickly Steam

I would recommend that you re-post your question on the strictly steam forum. Hopefully Gerry Gill will respond, he has allot of experience with dual gas valves on vapor systems.

ttekushan_3

two and a half things

Since you will use the vaporstat to control hi/lo firing, don't forget to keep the original pressuretrol as a high limit safety.



A very important thing to remember is that you will have to adjust the low fire level properly. I usually adjust the low for a "steady" steam pressure hold after coming off high fire. So if you are set at, say, 8 oz pressure to trigger low firing, the low fire should hold the pressure at 8 oz or a verrry slow creep up in steam pressure. You will need a low pressure gage to read this. Add one to the system, but retain the existing 0-30 psig gage to meet the letter of the law.



The problem with low fire being too low is that if any radiators have not heated fully, decreasing steam pressure can mean a distant radiator could begin to run cold. So set the low fire to maintain pressure, at the very least.



The final thing is more of an extravagance, but it should be superior in controlling excess air at low fire. Assuming this is an atmospheric boiler and If your installer is willing (and I can understand him drawing the line at this point for liability purposes), he can close off the draft hood and install a barometric damper in the flue to control draft.



The damper must be of the bidirectional type, the kind that swings both inward and outward; It must be properly sized and installed in the proper position and orientation; and it must be adjusted with aid of a combustion analyzer.



With a damper you will gain some efficiency over using the draft hood at lower firing rates.



Terry

DAS

Moved to steam forum

I've reposted to the strictly steam forum. Gerry has given a wonderful reply - something that only the depth of experience could provide!



My thanks to everyone for their input and knowledge, it's really incredible.