Boiler pressure too low?

[twitch]

I have a Scandtec Solo 30 with a very small heating system. From the boiler room to the air handler I have two runs of about 50' pex, and the boiler holds about 41 gallons of water (no storage). When the boiler is at 60* C my pressure is at about 13 psi. At 80* C it is at about 18 psi. When I went away at Christmas for a few days, the boiler was cold, can't remember the temp, but was way below 60* C, and the pressure was pegged low. I do not have the water makeup hooked up yet, but with this small of a system, does the pressure sound about right? If I had the water makeup hooked up, it would have increased the pressure to 12 psi when cold, but I'm sure that it would have blown off when the boiler was up to temp. Looking for some input of similar small systems.

Thanks,

Scott

 

[jebatty]

If you have a properly sized expansion tank, you should have no issue with blowing the 30 psi pressure relief valve based on 12 psi cold boiler. Typical boiler operating pressures are about 12-20 psi.

 

[chuck172]

Be warned that the tarm pressure gauges can be notoriously out of whack.

 

[stee6043]

My boiler was 12 psi 100% cold (including tanks) and runs at about 20psi when everything is at or near max temps. So I operate somewhere in the middle when recharging the tanks...

 

[twitch]

Jim - I'm pretty sure I have the correct expansion tank size. The company I bought the boiler from supplied it, and they knew how I was setting up my system. It's the same size you would find in a typical oil boiler, baseboard heat system. Do you think I'm losing anything by not having the system at 12 psi at cold?

Chuck - Pressure gauge out of whack in what way, reads low / high, or just not very reliable?

 

[chuck172]

twitch, I just recently went through the pressure gauge problem. Mine was reading way too low
I called tarm and wanted a replacement. After being denied by a tech. I was told by the owner of Tarm that he will send me a new pressure gauge but not to expect accuracy as these particular gauges are known to be way off. His advice was to replace the gauge with a quality aftermarket one.
He was right, the replacement gauge sucked too!

 

[jebatty]

Do you think I’m losing anything by not having the system at 12 psi at cold?

No to maybe. If low psi results in the upper reaches of your system not being filled with water (closed), then your air vents may allow air to enter the system, and each air entry includes CO2 and other impurities, which I think can result in acid formation. You may want to periodically test your boiler water pH to make sure it is in the 8.0-8.5 range.

If you have no harm in maintaining 12 psi (sufficient usually to cover a 2 story house), why not? No foul here.