Furnace always running/never satisfying

Hi,

Hoping someone can provide some insight, not extremely familiar with heating systems.
My furnace is running/blowing air almost constantly, it never seems to satisfy. Within about 30 seconds of it turning off it turns back on. The highest temperature I've seen coming out of the closest registers to the furnace is about 110/115 degrees which from what I've read around it should be much higher (130-140+).

• Oil forced hot air heating system
• Cape house in central MA (~1750 sq ft)
• Brand new Lyric T5 thermostat (had a regular digital thermostat before, no change due to the thermostat)
• Temperature generally set to around 67/68, can be set to as low as 62 all the way to 71 with no change in how frequent the furnace is running.
• Burner is a Beckett 7505 Genisys (Model "A", "AF")
• Furnace is a Olsen HML-80C
• Burner was cleaned less than a year ago, made no difference last season or this season since the heat was on
• Cold air return is in a hallway about 25 ft from closest register
• It takes about an hour to get the temperature on the thermostat to reach 68/69 from a starting temperature of 62/63 for example, I feel like it shouldn't take that long to warm the house 5-7 degrees.

Let me know if I'm missing any important information or if you have any ideas of what to look at for this.
I did just buy a Becket programming/diagnostic tool to plug into the burner as it doesn't have any display with its configuration right now (not in yet).

Thanks!

 

Welcome to the forums.

I don't really see any major problem with the system. The temperature of the heated air is furnace related. There is no set temperature. It can be as low as what you have and up to 150f. It is also dependent on the temperature of the return air.

I wouldn't call that an excessive amount of time for that much of an increase. It sounds like the furnace may be undersized for the house. A temperature rise test should be performed to see well the furnace is performing.

Your thermostat has a a narrow margin of swing in it. By Honeywell standards it turns the heat on 1 degree below the setpoint. Some thermostat have a larger swing for fewer close temperature operations. If the air is changing 1 degree that fast near the thermostat that would indicate that either a heat register is blowing on the thermostat or there is a large draft.

Was the stat set to Conventional forced air and Equipment type - oil ?

 

That sounds normal, it takes enormous amount of heat to warm up air and objects. After the air is warmed up and it cycles off the first time, it will still run a lot more than normal as the materials play "catch up" with the air temperature.

The colder it is out, the less surplus capacity available to warm the house back up.

Possible the burner isn't tuned right and is under-firing - need an oil tech to check that out with the right test tools.

 

specs show 75000 btu/hr output which should be plenty for a house of this size.

Correctly sized furnace btw, will run nearly all the time in the most extreme weather you get. most are bigger than needed.