existing zone valves and possible boiler repplacment

Frank_9

I have to give a price on a replacement steam boiler but I am a little concerned with the zone valves that are there . I have looked at the system measured the rediation got a size from my wholesaler and will pipe it according to the info in Dans great book . I have fired the boiler up and the return water comes back OK and the system is quiet on start up and also while it runs. There are check valves in the returns. the existing boiler runs on pressure waiting for a zone valve to open hence high fuel bills and the new homeowner not knowing anything about steam boilers never flushed the LWCO and cooked the rear section. It has been doped and is still running. the zone valves leaked by a little overheating the house just a little and I am thinking that is the reason the water returns so well.( I am planning on replacing the valves} I am planning on replacing all wet returns and also putting in a 3/8 in. bypass around the zone valves to put pressure on the system to help the condensate return to the boiler. I am not planning on running boiler on pressure and of course no more than two pounds ,as a good friend says all it takes is a whisper of steam to do the job . Do any of guys see any bear traps in this scenario?Thank you
Frank