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Gas Boiler - Inadequate Heating - Seeking Feedback/Solution
wgardner26
Member Posts: 9
in Gas Heating
Hello – As the weather is beginning to get cold in the northeast I realize that I need to finally address a heating problem that we lived with last winter and quickly forgot about as the weather improved. Unfortunately, just like any problem, it is not going to get better by itself. Hopefully, the experts on this site can provide me some guidance.
Problem - Our boiler cannot maintain the indoor temperature above 65F when the outdoor temperature is below the mid-20’s. When the temperature drops to the low-teens, the maximum indoor is in the 60F area. The boiler will nearly run continuously and the boiler output temp never seems to get up to 120F on these cold days, which then doesn’t offer much heat capacity for the baseboards, especially near the end of the loops. This is not a recent issue, the heating system has been inadequate over at least the last few years, but seems to be getting worse.
System overview
• Crown CXE-5 150K BTU “input”, circa 1997, Nat Gas, conventional open combustion, power exhaust via 3” pipe through foundation wall, combustion air from basement (not tightly sealed)
• Four zones, one circ pump
• The aquastat is set at 190 (hi), 10 (diff), no low limit. No ODR.
• Tech inspected recently and found no obvious issues – outdoor temp in upper 50s. No air in system.
• Serviced/cleaned/inspected last fall – no issues except replaced leaking relief valve
• Aquastat replaced two years ago due to failure
House
Two story colonial, unfinished walk out basement, 3800 SF, built in 1998, northern NJ. Two story entry/foyer. 2x4 construction. Medium air-tightness. Bought house in 2006.
Previous owners had large wood stove in FR – might have masked poor performance of heating system. Heat loss calc per Slant/fin app: ~100K BTU. Heavy use of gas fireplace makes heat loss estimate via gas use challenging (seen posters provide analysis using gas bill and degree days).
Zones
(1) indirect hot water (41 gal, Amtrol),
(2) 1st flr (105ft baseboard, 230ft loop), main living area (~2,100 SF)
(3) 2nd flr (63ft baseboard, 200ft loop), 3BR/2Bath
(4) 2nd flr (16ft baseboard, 110t loop) guest BR/laundry (doors typically shut w/ thermostat set at 62F).
Aside from my boiler potentially not operating property my thought is the first floor loop is too long. Includes 30ft of piping in unheated crawl space to supply family rm (350SF). 20ft baseboard. Floor and pipes are insulated. Three exterior walls, over 50% windows, 12ft ceiling, 8-40K BTU sealed gas fireplace.
Potential Solution – Replace boiler with high efficiency model. Add second zone to 1st floor or remove HW baseboard from family room and replace with electric (we primarily heat the FR with a sealed gas fireplace) – would remove 20ft baseboard and 70ft from overall loop. Concern is if we have the FR area on a separate zone, that zone will not run very often and the water in pipes will get very cold. Electronic heat option seems like a sub-optimal solution.
Once again, any insights/suggestions would be greatly appreciated before spending 10K on a new system. I received two quotes last year – neither performed a heat loss calc. If helpful, I can post pics of my system – not sure what items would be of interest.
Thank you.
Problem - Our boiler cannot maintain the indoor temperature above 65F when the outdoor temperature is below the mid-20’s. When the temperature drops to the low-teens, the maximum indoor is in the 60F area. The boiler will nearly run continuously and the boiler output temp never seems to get up to 120F on these cold days, which then doesn’t offer much heat capacity for the baseboards, especially near the end of the loops. This is not a recent issue, the heating system has been inadequate over at least the last few years, but seems to be getting worse.
System overview
• Crown CXE-5 150K BTU “input”, circa 1997, Nat Gas, conventional open combustion, power exhaust via 3” pipe through foundation wall, combustion air from basement (not tightly sealed)
• Four zones, one circ pump
• The aquastat is set at 190 (hi), 10 (diff), no low limit. No ODR.
• Tech inspected recently and found no obvious issues – outdoor temp in upper 50s. No air in system.
• Serviced/cleaned/inspected last fall – no issues except replaced leaking relief valve
• Aquastat replaced two years ago due to failure
House
Two story colonial, unfinished walk out basement, 3800 SF, built in 1998, northern NJ. Two story entry/foyer. 2x4 construction. Medium air-tightness. Bought house in 2006.
Previous owners had large wood stove in FR – might have masked poor performance of heating system. Heat loss calc per Slant/fin app: ~100K BTU. Heavy use of gas fireplace makes heat loss estimate via gas use challenging (seen posters provide analysis using gas bill and degree days).
Zones
(1) indirect hot water (41 gal, Amtrol),
(2) 1st flr (105ft baseboard, 230ft loop), main living area (~2,100 SF)
(3) 2nd flr (63ft baseboard, 200ft loop), 3BR/2Bath
(4) 2nd flr (16ft baseboard, 110t loop) guest BR/laundry (doors typically shut w/ thermostat set at 62F).
Aside from my boiler potentially not operating property my thought is the first floor loop is too long. Includes 30ft of piping in unheated crawl space to supply family rm (350SF). 20ft baseboard. Floor and pipes are insulated. Three exterior walls, over 50% windows, 12ft ceiling, 8-40K BTU sealed gas fireplace.
Potential Solution – Replace boiler with high efficiency model. Add second zone to 1st floor or remove HW baseboard from family room and replace with electric (we primarily heat the FR with a sealed gas fireplace) – would remove 20ft baseboard and 70ft from overall loop. Concern is if we have the FR area on a separate zone, that zone will not run very often and the water in pipes will get very cold. Electronic heat option seems like a sub-optimal solution.
Once again, any insights/suggestions would be greatly appreciated before spending 10K on a new system. I received two quotes last year – neither performed a heat loss calc. If helpful, I can post pics of my system – not sure what items would be of interest.
Thank you.
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Comments
3800 sq. ft. should require less than 95k btus at design temp. Your BBs are capable of emitting about 90k btus @ 170* AVERAGE SWT. Your boiler should have an output of about 120k btus and allowing for a piping loss of 15%, that would give you about 102k btus going to the BBs.
When you say you're only getting 120* SWT during cold weather, that definitely suggests something is wrong at the boiler.
I wouldn't replace any equipment until someone can properly diagnose what the problem is.
Can you post some pics of the boiler, it's near piping, and the controls?
You can choose to do what you want, but you cannot choose the consequences.
This chart should help.
Bob
Vaporstat with a 12oz cut-out and 4oz cut-in
3PSI gauge
"Zones
(1) indirect hot water (41 gal, Amtrol),
(2) 1st flr (105ft baseboard, 230ft loop), main living area (~2,100 SF)
(3) 2nd flr (63ft baseboard, 200ft loop), 3BR/2Bath
(4) 2nd flr (16ft baseboard, 110t loop) guest BR/laundry (doors typically shut w/ thermostat set at 62F)."
Based upon your info and the pics shown I am going to assume;
1. That you don't have a problem with hot water
2. The second floor zone (guest and laun) would heat fine.
3. The other bedrooms on the second floor would get warmer than 60 if none of the other zones are on.
Based upon some quick calcs, the first floor needs about 6 gpm and almost 19' of head. The head loss can be alot higher due to the pressure drop of the zone valves, just a guess at the Cv of the valve adding about 6' of head.
The 007 that is there can get you 6 gpm but only about 9' of head. So whats going to happen is the temperature drop will be large. Add in the other zones and at about 9gpm and 15' foot of head design-wise, we are under 8' of head. Also with the circ on the return pumping into the expansion tank hurts the performance.
So, several options:
1. need a bigger circ like a 0014 or a 0011(but will be noisy)
2. Split the first floor into two loops, can still be one zone but by splitting in half, the head loss will go down drastically. If you want to make it a new zone, go ahead.
3. Move the circ to pump away from the expansion tank. This is not a fix just a better practice if you are doing any of the above repairs.
Dave H
The gas meter may clock correctly, you would have to open all zones to keep the boiler running before..................................
it possibly goes off on high limit, the vent inducer will probably keep running making one believe that the boiler is still on. This has fooled many people with hot air furnaces as the blower fan noise covers the fact that the burner is off on high limit for a few minutes until things cool off.
If the issue was lack of flow through the baseboards, I would expect the boiler to be frequently reaching the high limit setting. If it is running all of the time and never reaching the high limit, something is limiting the boiler output. I agree with the other guys - check the gas consumption.
You mentioned un-insulated crawl space, does that space have outside air vents thru foundation wall. Those are often overlooked in the winter and are quite a heat loss item.
The result of the gas usage chart was 36 CF/ HR (50 sec rotation) with all zones active and no other gas appliances. Is this roughly equivalent to 36K BTU/HR (saw a conversion online)?
Yes, good hot water and heat to smallest heating zone.
The first floor zone splits off the same return as the hot water rather than having all four zones directly tied into the return manifold - is that correct? Picture included (1st flr zone is on the far right).
Circ pump is a TACO 007-F4.
Pic of temp/pressure gas included from test I just ran. Temp dropped quite a bit due to cold idle loops hitting the system.
Can back pressure adversely impact the heat output? I have included a picture of the boiler exhaust.
Thank you all once again.
If not then could there be LP orifices in the boiler or a real problem with NGas pressure.
Did the dial stop at all during clocking? If not, then the gas flow to the boiler is severely restricted. That could mean the line is too small or the pressure is too low.
If the dial stopped during clocking, then something is shutting the boiler off and your reading is invalid.
I agree with Dave that your probably under-pumped. But that's probably a secondary issue if your readings are correct.
You can choose to do what you want, but you cannot choose the consequences.
If I have a gas flow problem then who would handle - HVAC tech or the gas company?
Thank you.
That should get you some response.
Is your meter right at the house?
You still need a contractor who would clock the meter just like you did, then check the gas pressure at the burners, after the gas valve.
Please let us know the results. Thank You.
Based on your findings then if under fired you need to contact a professional to check gas pressures inlet and outlet to the gas valve.
Meters by the way never run fast they actually slow down over time. That meter looks pretty old as it still has the number index instead of digital so have the local gas company check it and they should also be able to check the gas pressure.
It would still be a good idea to have a professional check you system.
So you still need the pro, to check the pressure on both sides of your boiler gas control valve. He might look at the size of orifices on the burners.
If he thinks that none of this could happen, call someone else.
It the 7"WC was with the furnace running it could be the gas valve or a gas orifice problem.
Bob
Vaporstat with a 12oz cut-out and 4oz cut-in
3PSI gauge
Could be possible that the pressure switch is cutting out so watching the flames or watching the gas meter for a while makes sense.