Pressure vs Temp cut out

btc

The recent discussion on Pressuretrols got me thinking...Is it normal for one pipe steam to never cut off on pressure--only on temp? I leave my Honeywell T8090[3 yrs old] stat on 66, no setback, anticipator set at 1.2. System cycles on about every 4-6 hours in winter depending on outside temp [avg mid 30s]--runs for about 45 minutes [cuts on at about 64 deg. and cuts off at 66, then overshoots 1-2 deg.] Rads heat relatively uniformly between 3/4 and all the way depending on outside temp. Wondering if never cutting off on pressure is normal characteristic? Is there a way test if pressuretrol is even working?

System includes: 1950's Gas boiler-108K BTU output, 390 sf EDR cast iron rads, Gorton #1 vents at end of each main, insulated pipes, older mercury P404A Pressuretrol with pigtail. Cut-in set at approx. 0.5 and differential of 1. Near boiler piping looks exactly like installation manual instructions. Combination of Hoffman 40 and 1a vents on 10 rads.... Thanks in advance for any thoughts. Brian

Al Letellier

Pressure cut out

One would think that a 45 minute run cycle would build enough pressure to cycle off the pressuretrol. Replace the gauge to make sure it's functioning and watch the pressure. You are certainly producing the steam to heat the house, so I would suspect bad vents or an inactive pressuretrol. Check the pigtail to make sure it's not plugged. That long a cycle could be building high pressure in the system that isn't safe to leave alone. If in doubt, hire a pro to check it out. Be safe as well as comfortable.

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btc

Ptrol cleaning

Al, much thanks for the advice. I cleaned out the brass pigtail and pressuretrol after seeing your post--pigtail was totally clogged with sludge. Cleaned out both units and hooked back up. Do you have a sense of how this might affect the system operation, if both are now functional? Thanks.

steve_6

GAUGES

Get a gauge that reads in ounces. Make sure that its protected by the siphon tube

Al Letellier

operations

You should see a noticeable decrease in boiler run time and fuel comsumption. With the boiler running with a working pressuretrol, a more likely cycle time would be 5-10 minutes depending on the size of the boiler and connected load, but you will definitely notice a change. The system will heat better and more consistantly, because all the latent heat is given off when the steam condenses on the cooler surfaces of the radiator. This will happen more evenly when the boiler cycles off on pressure and allows the steam to condense and return to the boiler more easily. With the boiler running wild, there is always some pressure in the system, messing up the normal sequence. Glad to be of assistance.

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