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#129856 - 11/16/04 08:43 PM Old oil/boiler/hot water furnace doesn't heat well
Oregon Offline
first timer

Registered: 11/16/04
Posts: 3
Equipment: Wayne Model E - oil burner / boiler - hot water fin-radiator baseboard units. Circa 1956. Simple, almost no controls. It has a thermostat for air temp, an aquastat (boiler temp?) and two gauges, one for "altitude" (pressure?) and one for water temperature (Farenheit).

Problem: House doesn't stay warm when it's really cold outside and furnace runs only 2 minutes at a time.

Suspicion: Furnace is not adjusted correctly or aquastat out of calibration.

2 years ago I bought the house. For the first 2 winters, during the heating months, the water temp gauge read 135-140 or so degrees and the furnace came on at least once per hour (but probably not 2x per hour.) Radiators all got hot and the house would heat up in about 20-30 minutes of furnace operation. Things were good until it was 20 degrees outside, which caused the heat to max out at about 64 degrees room temp. Setting the thermostat higher would not make the furnace come on more frequently.

I had the thermostat replaced on general principles last year, with another Honeywell dial type unit (same as orig.). The adjustment on the thermostat is currently set to .4, which is what the furnace model called for in the 1956 manual.

I had a service person familiar with boiler systems come out recently (from an oil company recommended by a furnace sales company recommended by the mfgr.). He said my aquastat was set to around 200 degrees, and that that was bad, so he set it down to 180. Note that the water temperature never nears 180 at any time prior to or after his service call, according to the temp gauge on the furnace. In fact, it never hit 140 when the aquastat was set to 200.

Now, after the adjustment to the aquastat, the radiators get warm but not hot (they used to get hot enough that you wouldn't want to touch them for long). The gauges on the furnace now read around 12 "altitude" and 115 degrees water temp at rest. The thermostat is set to 70 and the furnace comes on when the therm reads 68. It then runs for about 2 minutes, reaching a water temp of 118, then cuts off. The water circulator runs for about a minute before the furnace ignites but doesn't run after the burner kicks off again.

The service person said we probably should replace the 50-year old aquastat during the spring service, but when I suggested we do it now, he said he didn't think it could be causing the problem, because he said it's just a safety cutoff for if the water in the boiler gets too hot. I wonder if it's so far out of calibration that it's the real culprit.

The combustion is great and there doesn't seem to be any problematic air in the system. He replaced the oil nozzle in the burner.

Note about the water circulator: I have 2 switches on the furnace, on/off and auto/manual. The furnace is set on and auto. We tried running the furnace on "manual" which made the circulator run all the time, but the water temp fell to 90 degrees after 6 hours and the house temp fell to about 64 degrees.

Thank you for any suggestions.

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#129857 - 11/16/04 08:59 PM Re: Old oil/boiler/hot water furnace doesn't heat well
HeatPro Offline
Carpal Tunnel

Registered: 07/30/04
Posts: 28022
Loc: South New Jersey
Easy enough to try a test. Set the thermostat all the way up, if the burner stays on and warms the water in the boiler to 180F (don't be concerned at this time whether it heats the house up or not for this test), then the aquastat is good (provided there is no other reason for the burner to go off), if not, it is bad, so replace it.

If the water finally heats to the high limit at 180F, but the water is not leaving and coming back to near the boiler at 160F, then there is a water circulation problem.
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#129858 - 11/16/04 09:19 PM Re: Old oil/boiler/hot water furnace doesn't heat well
Fuelpump Offline
first timer

Registered: 11/13/04
Posts: 15
Loc: Planet Earth
Problem: House doesn't stay warm when it's really cold outside and furnace runs only 2 minutes at a time.

There are a few things you want to look for. House doesn't stay warm when its could outside. ( 1 ) Check to see what size nozzle is being fired against manufactures spec on boiler, make sure your boiler is not being under fired. ( 2 ) make sure your system is not air bound, one can usually hear water running through the baseboard if so. ( 3 ) make sure your circulator is working. ( 4( your aquastat may not be sending power to your circulator in which case it needs to be replaced. You said your thermostat was replace last year so I'm assuming its ok however turn your thermostat up an make sure its closing the circuit on the relay that has tt on it. If nothing happens then jump tt on the relay an if burner comes on its your thermostat or the wire from thermostat to relay.However it sounds like a control problem to me.



Edited by Fuelpump (11/16/04 09:29 PM)
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#129859 - 11/16/04 09:37 PM Re: Old oil/boiler/hot water furnace doesn't heat well
superheat Offline
fanatic

Registered: 03/23/04
Posts: 440
True fuelpump. A control problem. If circs are working and she goes down to 90 deg and still no burner.......there ya go. Time for a new aquastat. It wouldn't be a bad idea to replace the well at the same time, it might have some scaling on it.
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#129860 - 11/16/04 10:02 PM more info: test results
Oregon Offline
first timer

Registered: 11/16/04
Posts: 3
OK, I tried the test: Turn thermostat all the way up.

Results

* After 30 minutes, the gauge on the furnace reached 175-180 and the furnace shut down.

- Pressure was 12 alt.

- House temperature went up 2 degrees to 72.

- All the radiators were warm but not really hot.

-------
Notes: There are 2 thermometers on the pipes, above and below the TACO water circ pump. The top one ended up around 155 and the bottom one was around 110 at the end of the 30 minutes.

The TACO hums and vibrates a bit, but it makes the kind of hum a sewing machine does before it engages the needle.

The first year I had the house,a little water noise was noticable in the radiators at the beginning of the cycle, but now I don't hear any water unless I'm near the TACO. It sounds like a trickle. I don't think the system has been bled for air in those 2 years, though, so maybe no noise is not a good indicator of no air.

Thanks very much for your suggestions so far.

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#129861 - 11/16/04 10:10 PM Re: more info: test results
HeatPro Offline
Carpal Tunnel

Registered: 07/30/04
Posts: 28022
Loc: South New Jersey
You show that the burner and high limit aquastat are seemingly OK. the radiators only getting to 150 while the boiler gets to 180F shows that the boiler thermometer is wrong or the circulator is not moving water fast enough. Check the boiler temperature by measuring the water temperature leaving the boiler with a thermometer. It could be that the thermometer is wrong and the high limit is turning the burner off at the lower temperature with the circulator moving enough water.

When all is OK the first radiators in the circuit should be at the same temperature as the boiler.
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#129862 - 11/17/04 04:18 PM Re: more info: test results
Fuelpump Offline
first timer

Registered: 11/13/04
Posts: 15
Loc: Planet Earth
It would be easier if you could let me know what type of aquastat you are working with. For instance is it an 8124 control or a 8148 control or a 8182 h or j control. I agree with Heat pro on a few points he had mention but the fact that your boiler shuts off on high limit after reaching 175 to 180 after a half hour tells me the boiler is under fired meaning the nozzle size is to small. Now having said that when you talk about your circulator it sounds to me that you have a Taco 110 which has a motor a bearing assembly an also an impeller it could be that the impeller has disintegrated not circulating the hot water from the boiler. However you mention the gauges on the return pipe read 155 on one of them an 110 on the other tells me your low limit is not maintaining boiler temp an should be replaced. Like I said if you tell me what type of control you have I can tell you exactly what the problem is.

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#129863 - 11/21/04 01:09 PM Re: more info: test results
Oregon Offline
first timer

Registered: 11/16/04
Posts: 3
The aquastat is a Honeywell L4006A
It doesn't have a lower limit setting/control for water temp, only a high limit one.

the manual says an 80 degree nozzle is needed.
the repair guy put in somethin ghe calls a .85-80 , 35LoA 8001 or something similar (his writing is debatable, so the number could be 3SL0A 8001

I have a TACO horizontal model between 100-120 that had seals replaced in 1969. It is original eqt. from 1956.

I did another test: I turned the house thermostat all the way up.
I turned the furnace from Auto to Manual
and after about 7.5 hours this was the result:

house: 76 degrees
radiators: hot
pressure 15 alt.
water temp gauge on furnace: 170
top thermometer (above TACO) 150
bottom therm 90 degrees.

I then reset the furnace to run on automatic.

Today it's 35 degrees outside, and with the thermostat set on 72, in the morning the house was 64 degrees. The furnace read 175 or so on the guage when I checked it and it was off. Radiators were faintly warm. I kicked the thermostat all the way up, and in a couple of hours the house temp went up to 66 or 67 degrees.

Question: is the TACO supposed to be circulating water all the time, even when the burner is not firing? Or is it a cyclical system meant to heat up water, circulate, dissapate heat, repeat?

Question: could the TACO be functioning but not very well, causing inefficient water circulation? If yes, should I replace or rebuild?

Question: Could the furnace be staying off too long between cycles because the water temp in the boiler is kept high for some reason (for example, because it just sits there instead of being emptied into the system?

Note that the heating problem began before the nozzle replacement and continued after. I think the nozzle is not the problem. It was replaced because the furnace stopped running at one point, which fixed that problem.

Thanks for your advice, I sure do appreciate it.


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