HB Smith (propane) Boiler model# PGV 100 - W - 7 HSI

[Chris-man]

Dear Appliance Gurus,   I am the proud new owner and occupant of a duplex that has 2 hot-water-baseboard propane boilers. I am hoping to find assistance with getting these things working effeciently before Vermont Winter sets in. While crawling around in the dank house underbelly I first found the HB Smith (see model # above) backflow preventer leaking.  I removed and cleaned the old one and the leak continued so I bought a new valve ($49.50)and installed to find the leak continues as before. Which has lead me to the question of 1) sediment making both valves not work and 2) the zone pressure of 35+ PSI being too high or being out of correspondence with the domestic water pressure.  Any of this making sense?  I also have questions about antifreeze, purging, and more so please comment. Your help will be appreciated. Thanks! 

[AccApp]

There should be some sort of automatic water pressure regulating device. It is no longer functioning but allowing full domestic pressure into the system. I normally expect about 14 psi at normal temps (pressure will increase with temp). If a brand new backflow is leaking you have excessive pressure. Can you post a pic of the incoming and outgoing water lines? Every system is different.

[Chris-man]

Dear AccApp,  While flushing the boiler-side pipe I effectively lowered the excess pressure to about 25 pounds. At this pressure, you are right, the backflow preventer slowed to a drip. But as luck would have it, I created a leaky "reducing valve" which I now must replace. FW Webb gave me the reducing-valve name for the pressure control device you mentioned. I think It'll work properly when I get the reducing valve installed.  I'll update you but must plan a trip to glorious Springfield, VT to FW WEBB first.  Lastly, do you know how to add antifreeze to the zone plumbing?  Also, how do I test for the concentration of anti freeze?    Thanks.

Sorry, I am not facile with getting pictures--yet          domo

[hvacdrd]

The anti-freeze used in a boiler system is not the same as that used in your car but you can use a similar glycol tester with a sample from your boiler. The anti-freeze is Propylene Glycol with trade names such as Pro-Tek , Noburst or Burst-Kontr'l.

Adding it depends on current freeze protection levels. Typically if the system already has glycol and the freeze level is ok, using a 50/50 mix you will have to pump it into the system using an external pump. Of course using a higher concentration if the current freeze level is insufficient.

As for the pressure issue AccApp stated it is normally around 12-16psi. To determine if it is a bad fill valve turn of the domestic water supply inlet, drop the pressure down to 12. Turn on the domestic water supply and if the pressure climbs back up to 30 replace the fill valve. 

If it holds steady check the expansion tank by turning off the domestic water inlet, drop pressure to 12 & fire the boiler up to operating temp. If the pressure jumps up to 30psi & starts relieving then you have an expansion tank problem.