Hot water furnace won't go above 65?

Old 01-31-08, 08:56 AM
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Cool Hot water furnace won't go above 65?

Hello, I am having problems with my hot water furnace. It's a closed loop system. The furnace heats good up to about 60-62. If you set the thermostat any higher the furnace ignites and runs constantly, it can never reach the 72 setting on the thermostat. The furnace does shut off, there must be some safety kick off on it. When it comes back on it runs and runs but can't bring the heat above the 60-62, it has to run constantly to keep the heat there. The system has a regulator on the line coming in from the city water. The regulator has leaked in the past, we worked on it but did not replace it. The lines from the furnace and the return lines as well as the lines throughout the house get so hot you cannot touch them. You can feel the heat radiating off the baseboards. We have bled all the lines, there was air. We have recharged the expansion tank to 12-15 psi. We replaced the pump on the system. We set the temp on the furnace from 180 up to 195 and still no heat? We have put a couple different thermostats on, still no improvment. Do we need to replace the regulator on the line coming in? Maybe there is problems with the expansion tank? We're stumped because the lines get so hot and you can feel the heat coming off them, but we can't get above 60-62 and the furnace running all the time to keep it there? We have used an air hose and brush to clean all the baseboards and straightened out the heat deflectors/fins. I look forward to any suggestions. Thank you. Joe
Old 01-31-08, 09:32 AM
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I’ll just toss out some ideas randomly…

The heating system’s job is simply to replace the heat that leaks from the building at around the same rate that it is escaping. That said…

What’s your heatloss number and what is your boiler rated for? The heatloss number can be calculated using free software from SlantFin’s web site.

Is your house properly holding its heat? Are any doors or windows not closed, not fitting properly, or normally should have storms installed, etc?

Has any work been done on the house that may have jeopardized your insulation? For example, my A/C installers left all the insulation lifted above my dining room when they ran their linesets – luckily I noticed it a month or two later.

Has you boiler been properly cleaned and tuned recently? If it’s all caked up inside, then the coasting on the wall linings end up insulating the water passages from the heated gases instead of allowing them to properly transfer the heat.

Have you noticed an increase in the volume of fuel you have been burning? Not the dollars that are obviously up, but the actual number of gallons or cubic feet depending on what you are burning.
Old 02-01-08, 12:45 PM
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62 degrees

If the boiler is shutting down on limit and pipes and rads. are hot ,check the return lines to make sure the pump is turning, not just the motor but the impeller it's self.
Old 02-01-08, 02:32 PM
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Are all the baseboard covers on, end caps in place and dampers (if supplied) open? Is there a few inches between the carpet and the baseboard cover?
Did it heat OK last year and eralier this year? If so, what changed?
If supplies, returns and baseboard are hot then it must be an air flow issue or as who stated heat loss greater then heat input.

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