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Re: Drain back with evacuated tubes
Any of the U tube type evac could be used as a drainback if you slope them
The issue I had is that U tube us the small diameter, around 3/8 and doesn’t always drain completely mine went two winters, froze on the third
If you can find a heat pipe style with a smooth header, no low spots. It could work
Keep in mind stagnation temperatures in evac tubes can go well over 500F! So when fluid first hits them, some serious expansion, flashing to steam and noise.
The issue I had is that U tube us the small diameter, around 3/8 and doesn’t always drain completely mine went two winters, froze on the third
If you can find a heat pipe style with a smooth header, no low spots. It could work
Keep in mind stagnation temperatures in evac tubes can go well over 500F! So when fluid first hits them, some serious expansion, flashing to steam and noise.
hot_rod
1
Re: Stupid question regarding furnace air flow
With only 3 wires on the 2 second floor thermostats, it seems like it might be an old Trol-A-Temp Master/Slave zoned system. (Only the first floor thermostat can switch between heat and cool.)
Look around the furnace for a zone panel and zone dampers in branch ducts. Possibly a Summer/Winter switch.
If that's the setup, it could be a bad damper.
There is AC, so High speed fan is probably connected here. Most furnaces using PSC motors offer multiple speeds. If the heat speed is on Low (usually Red wire), then you can increase it to Medium.
There is a rating listed on heat rise for the furnace, so just make sure it's not out of range if you make a motor speed change.
Look around the furnace for a zone panel and zone dampers in branch ducts. Possibly a Summer/Winter switch.
If that's the setup, it could be a bad damper.
There is AC, so High speed fan is probably connected here. Most furnaces using PSC motors offer multiple speeds. If the heat speed is on Low (usually Red wire), then you can increase it to Medium.
There is a rating listed on heat rise for the furnace, so just make sure it's not out of range if you make a motor speed change.
HVACNUT
1
Re: Boiler High Limit set too low?
Thanks @Jamie Hall that is good to know. Even under normal circumstances, I think the boiler left to its own devices rarely gets above 135 when the weather is warmer than 20 degrees - and it only does so because of the existing mixing valve. The mixing valve is only on the return line to keep it above 122 degrees. Before that was installed, it would run for 45 and never get above 115-120 degrees and satisfy the house Tstat. We had -5 degree days in a row and the house was satisfied and the highest the boiler could get the water temp was 139/140 for an hour, boiler only ran 8-9 hours those days.
I'll put it back to the previous max of 143 (which it never hits) and put some sensors on the supply side to log max temp needed based on outside temp. Would be an interesting chart.
I'll put it back to the previous max of 143 (which it never hits) and put some sensors on the supply side to log max temp needed based on outside temp. Would be an interesting chart.
DJDrew
1
Re: one pipe steam Radiator vents
Interesting. Is this a continuous suction? Or is it pulses at specific radiators. I honestly can't think of a mechanism which will create a continuous suction at a vent or even an open pipe so long as the boiler is firing, unless there is an eductor or vacuum pump on the system -- and that wouldn't be found on a one pipe system (and is rare on residential two pipe systems...).
If it's in pulses, and different at different radiators, there is a possibility that the problem has to do with pockets of trapped water in the piping, which could also cause the banging -- but that would only be very short pulses at specific radiators.
And... not that I doubt your observation, but double check. Are they really sucking, indicating a vacuum, or are they actually blowing?
If it's in pulses, and different at different radiators, there is a possibility that the problem has to do with pockets of trapped water in the piping, which could also cause the banging -- but that would only be very short pulses at specific radiators.
And... not that I doubt your observation, but double check. Are they really sucking, indicating a vacuum, or are they actually blowing?
Re: How accurate are the efficiency percentages claimed by the mod con boiler mfr's?
So? If a system radiation needs more than 127 degrees water temperature in the radiators, it would seem that there is no condensation of exhaust gases. This being the case, why recommend a mod con boiler?It's the return temperature at the boiler that determines how much it condenses.
The dewpoint of the fuel depends some want on the CO2, which is what the combustion analyzer reads to come up with efficiency, and the setting that the boiler manufacturer wants.
My Lochinvar asks for CO2 9- 10.5% on high fire NG, 8.8- 9.5% on low fire as an example.
Also some Viessmann slides explaining condensing mode.
My Lochinvar Knight allows up to a 35∆, so to obtain a 120 condensing temperature I could run a 155° SWT, return is at 120 and condensing starts.
hot_rod
2
Re: Which is the C (common) terminal on a Honeywell Aquastat L8148E?
this is all that is needed
TV on L8184E control = R on the NEST
Z on L8184E control = C on the NEST
T on L8184E control = W on the NEST
Don't change any jumper between Z and W on L8184E control. Leave it where it is.
Must I remind everyone that Electric is colorblind and it can't read either. This works for the control that @erikengquist shows in the picture. L8148E. It does not work for other controls like the L8148A
TV on L8184E control = R on the NEST
Z on L8184E control = C on the NEST
T on L8184E control = W on the NEST
Don't change any jumper between Z and W on L8184E control. Leave it where it is.
Must I remind everyone that Electric is colorblind and it can't read either. This works for the control that @erikengquist shows in the picture. L8148E. It does not work for other controls like the L8148A
Re: Troubleshooting of recurring overheating events
Hello @zxcv_1984,
Intermittent problems can be the worst. A lot of time can be spent trying to catch them in the act. Sometimes it helps if whatever stimulus is causing the problem can de determined. Is it Weather related, water ingress, amount of use, vibration, loose connections, chafed wires, etc.
If the sensors and their electrical connections are all fine, wouldn't the controller shut the pump off correctly to limit the storage tank temperature ?
If the relay that controls the pump was sticking, for example, how would the controller shut the pump down for an overheating event, it would need a secondary means.
Is the normal operating high limit temperature setting too close to the overheating limit temperature setting ?
Intermittent problems can be the worst. A lot of time can be spent trying to catch them in the act. Sometimes it helps if whatever stimulus is causing the problem can de determined. Is it Weather related, water ingress, amount of use, vibration, loose connections, chafed wires, etc.
If the sensors and their electrical connections are all fine, wouldn't the controller shut the pump off correctly to limit the storage tank temperature ?
If the relay that controls the pump was sticking, for example, how would the controller shut the pump down for an overheating event, it would need a secondary means.
Is the normal operating high limit temperature setting too close to the overheating limit temperature setting ?
109A_5
3
Re: How accurate are the efficiency percentages claimed by the mod con boiler mfr's?
@pecmsg: thanks for your comment; that's what I think too. I don't think I have ever seen my car mileage even close to the advertised mileage. Probably the mfr is using a brand new boiler and if it doesn't give them the result they want, they are going to try another until they get the result they want. What about a boiler that's been used for one season let alone 10 seasons(half way through the life cycle)? Won't the efficiency go down (even a little) as the the little spaces in the heat exchanger get filled up with debris?
john123
1
Re: How accurate are the efficiency percentages claimed by the mod con boiler mfr's?
The return water temperature drives the boilers efficiency, they can and do reach high 90% efficiencies
Cycle efficiency and system efficiency is another discussion
hot_rod
1