Wall Tstat controls boiler gas valve

HandyMike

Hi guys.

I have a 99 year old boiler. It looks to me like it was converted from coal, to oil, to gas.

It has a 1/12hp B&G pump on it as a retrofit.

I have been in my house for 10 years, and on Thanksgiving the pump coupler failed, with a spectacular noise.

Anyway, the tech replaced the coupler, and gave me a due diligence sweep with a CO monitor. 

All passed.



I have had only one service call in 10 years.  I am satisfied. 



Anyway, my pump is wired to run constantly.  The thermostat controls the gas valve.  This intrigued my tech...



Is my system OK?  Is is safe?

Charlie from wmass

It is safe

But not very efficient with a 100 year old boiler. A relay can be added to turn both the pump on and off and the gas valve. The draw from that pump 24 hours a day is adding to your electric bill plus when the boiler is not firing it is acting like a heat pump from your house to the chimney. Now if the pump turns on and off you may find other issues, like uneven heating.

Jean-David Beyer

Safe? I wonder.

If you have it serviced only once every 10 years, a lot could go wrong with it over a 10-year period. I would not wish to breathe CO for that long, for example. Maybe my former contractor was right that gas boilers do not require maintenance, but I disbelieved him.

zacmobile

old boiler

I have serviced quite a few set up such as this where I am, most are circa 50's. The t-stat turns on the gas valve and the pump is enabled by an aquastat on the supply which kicks in at usually 140deg F. I suppose they set it up this way to let the boiler heat up before circulating, just like it's done on hydronic fan coils. Are you sure yours isn't set up like this?



PS: why in the world does the spell check pick up on "hydronic" & "aquastat"?

Tim McElwain

It was more than

likely an old gravity system. When we converted those systems to gas we found that it was better to have a constant running circulator to keep the water moving and try to keep somewhat even temperature in the system. I assume you shut the power off in the summer time?



There are other options to this system such as installing an aquastat to maintain a low limit temperature in the boiler and then bring circulator and burner on together through a relay.



If you are happy with it the way it is then leave it alone.



Just a final note it may be time to start thinking of a new boiler and the old gravity system work great with the new modern Mod/Con boilers.

Ironman

Spell-check

Zac,



I've wondered the same thing. It seems odd that on a blog dedicated to hydronics the spell-check doesn't recognize that word.

HandyMike

Thanks for your help, guys.

I figure 1/12 hp X .750kw/1hp X $.15/kwh X 24h X 30d = $6.75/mo.  Not that bad. 

I do shut the system off in the summer.

I am not sure how much heat the pump will pull from the house, because for heat to transfer from the house to the chimney, heat must be transferred from the rooms to the radiators.  For that to happen, the radiators need to be cooler than the rooms, which is not the case most of the time.

I am thinking of a new boiler, but I am also thinking about a chimney liner, asbestos abatement, lightning sensitive electronics, etc., etc., etc.

I guesstimate a new boiler will be $7,000.  I have a lot of home projects competing for those dollars, namely rehabbing windows and a new roof (with added attic ventilation so I can lower my AC bills).