Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.
Best Of
Re: HTP Boiler short cycle
The step modulation will likely not help your issue and will delay the response to the building. You want the boiler to immediately go to whatever level is necessary to heat the building on the design day. If your heatloss is 40K, that's all the output the boiler requires. The CH limit will accomplish this.
I believe you will have quite a bit of success with a CH limit of 55 (assuming a 40K heatloss).
I guarantee that you will have success with a CH limit of 45. HOWEVER, you MIGHT need to raise it if you get near the design day. Remember I am making an assumption on your heatloss. If you know what you have you can calculate the CH limit appropriately. Figure the output of the boiler is 70K and calculate based upon your own heatloss for the building.
I believe you will have quite a bit of success with a CH limit of 55 (assuming a 40K heatloss).
I guarantee that you will have success with a CH limit of 45. HOWEVER, you MIGHT need to raise it if you get near the design day. Remember I am making an assumption on your heatloss. If you know what you have you can calculate the CH limit appropriately. Figure the output of the boiler is 70K and calculate based upon your own heatloss for the building.
LRCCBJ
1
Re: Residential boiler fire/heat won't turn off
Remove the White wire from TH-W and put it on 24V (GROUND).
Take the Black wire that was on 24V (GROUND) and put it on 24V.
Take the Black wire that's "just hang in the air", and put it on TH-W.
Turn off the power first of course. Hope nothing shorted the way it is.
No jumper needed for the vent damper molex?
Take the Black wire that was on 24V (GROUND) and put it on 24V.
Take the Black wire that's "just hang in the air", and put it on TH-W.
Turn off the power first of course. Hope nothing shorted the way it is.No jumper needed for the vent damper molex?
HVACNUT
1
Re: My Honeywell L8124C/R8184G4009 Operation Question
Exctly right Mike. With one addition that often gets forgotten when adding circulator zones. The low limit has two functions.
#1 As you mentioned, is to have a lower High limit (or operating limit) to maintain enough heat in the boiler to make DHW when there is no call for heat
#2 Is to place the DHW on priority. It does that with a Reverse limit which is a set of contacts that breaks when the temperature falls (better known as Makes On Temperature Rise). this reverse aquastat will stop the circulator from dumping all the hot water in the boiler into all the radiators in the house on a call for heat. Otherwise, If you were in the shower and the thermostat called for heat and all the hot water went into the radiators you would end up getting a cold shower. No One wants to take a cold shower (except your wife may want you to take one some nights, but that is another story). So the circulator pump will stop heating the home before the boiler gets too cold, then the burner can catch up to that operating limit temperature. Once the boiler is hot again the circulator can turn on to heat the home again.
Now this is a lot to follow so I like to break it down into sections.
Section 1 is the high limit. that will keep the burner from over heating the water in the boiler
section 2 is the low limit. This will maintain a minimum water temperature in the boiler Less 10°. So if you set it to 150° then the lowest temperature is 140° or the burner will come on.
Section 3 is the reverse that is connected to the low limit to prevent the circulator pump from stealing all the hot water
Section 4 is the relay that is connected to the thermostat. That will operate the burner and the circulator to heat the home unless something in section 1, 2 or 3 tells it not to.
That is the simple explanation of that control
Still want a to know why @JMGotts is asking the question. If they have a tankless coil boiler, and if the DHW is still being used. There is a lot of stuff that is not needed if that old coil was disconnected 10 years ago. Can we hear from you @JMGotts ? Enquiring minds want to know!!!
#1 As you mentioned, is to have a lower High limit (or operating limit) to maintain enough heat in the boiler to make DHW when there is no call for heat
#2 Is to place the DHW on priority. It does that with a Reverse limit which is a set of contacts that breaks when the temperature falls (better known as Makes On Temperature Rise). this reverse aquastat will stop the circulator from dumping all the hot water in the boiler into all the radiators in the house on a call for heat. Otherwise, If you were in the shower and the thermostat called for heat and all the hot water went into the radiators you would end up getting a cold shower. No One wants to take a cold shower (except your wife may want you to take one some nights, but that is another story). So the circulator pump will stop heating the home before the boiler gets too cold, then the burner can catch up to that operating limit temperature. Once the boiler is hot again the circulator can turn on to heat the home again.
Now this is a lot to follow so I like to break it down into sections.
Section 1 is the high limit. that will keep the burner from over heating the water in the boiler
section 2 is the low limit. This will maintain a minimum water temperature in the boiler Less 10°. So if you set it to 150° then the lowest temperature is 140° or the burner will come on.
Section 3 is the reverse that is connected to the low limit to prevent the circulator pump from stealing all the hot water
Section 4 is the relay that is connected to the thermostat. That will operate the burner and the circulator to heat the home unless something in section 1, 2 or 3 tells it not to.
That is the simple explanation of that control
Still want a to know why @JMGotts is asking the question. If they have a tankless coil boiler, and if the DHW is still being used. There is a lot of stuff that is not needed if that old coil was disconnected 10 years ago. Can we hear from you @JMGotts ? Enquiring minds want to know!!!
Re: HTP Boiler short cycle
It has honestly acted like this intermittently since install in 2017.When the boiler was originally designed and initially delivered in 2015, it had serious issues with the control logic. The boiler could not modulate quickly enough before it reached +5F. over limit. Then it would shutdown on limit and restart about one minute later.
HTP made several iterations of that control over the two years between 2015 and 2017.
When done, the boiler could respond properly to an instantaneous closure of two zones (out of a total of three) and it would NOT shutdown on limit. HTP decreased the response time for modulation and also increased the the margin to +12F over setpoint before a shutdown occurred.
The final result was truly excellent from the original starting point.
Sadly, most installations of this boiler in that time frame will suffer from the poor control logic and none of the installers can do much about it.
You can mitigate the issue to some degree by reducing the CH heating capacity. This is parameter 18:cb on the display. If you can heat the building with 40K BTU's (likely) set the parameter at 55. It's much easier for the boiler to modulate down from 40K then from it's maximum (72K). Step modulation (37:CM) will not help with this issue.
However, understand that this approach will severely limit your capability of recovery if you are inclined to reduce the building temperature overnight.
If you were to replace the control board, all issues would disappear.
LRCCBJ
2
Re: Two Pipe radiator plumbed in after the vent on the return
@Ted_Ryan
If it works ok and it likely will there is no need to relocate the vent. If you have a problem just stick a vent on the radiator return close to where it ties into the main return.
If it works ok and it likely will there is no need to relocate the vent. If you have a problem just stick a vent on the radiator return close to where it ties into the main return.
Re: Plumbing archaeology
Plumbarius...worker of lead. No, drum traps are prohibited in New installs. Mad Dog 🐕
Re: Hot water vent (!!) on steam main
It just won't work righ. It won't hurt anything except it will cause the system to not work as well as it should. Post some pictures of the system, a couple of radiators and a few boiler pictures including the boiler piping.
Re: Hot water vent (!!) on steam main
The wrong air vent will either prevent air from escaping the system impeding the flow of steam leading to longer heating cycles to satisfy the thermostat in addition to building pressure which may be sufficient to trip the pressuretrol leading to short cycling of the boiler. If the pressuretrol doesn't work due to a clogged siphon loop (pigtail) or is set to too high of a cut-out pressure the built up pressure may damage the air vents on the radiators. Higher pressures lead to wet steam from the density of the steam being forced out of the boiler which may cause the water line in the boiler to drop lower than usual.
If the air vent leaks there will be a drop in the water level in the boiler over time which can lead to various problems; most commonly excessive make up water being added.
The better your main air vents are the more efficiently and quietly the system will run. Steam needs air out of the way in the pipes to get to where it wants to go and good vents will also keep steam trapped in the pipes so that you don't lose water.
If the air vent leaks there will be a drop in the water level in the boiler over time which can lead to various problems; most commonly excessive make up water being added.
The better your main air vents are the more efficiently and quietly the system will run. Steam needs air out of the way in the pipes to get to where it wants to go and good vents will also keep steam trapped in the pipes so that you don't lose water.
Waher
1
Re: Two quotes for combi boilers for radiant and DHW
Nothing to lose by adding some pressure. Below 30 psi.You increase pressure by lifting this metal hoop on the pressure reducing valve. It basically allow the pressure in the building to bypass that valve, so lift it carefully as you watch the pressure.
Download the manual for more operatinginfo.
So I should try to build pressure up to 25 psi (by lifting metal hoop on pressure reducing valve) and then seeing if pressure drops? Because the reducing valve seems to be set around 11 psi, I assume no new water will enter system until it gets to around 11 psi?
hot_rod
1
Re: Two pipe steam radiator problems!
I bet it's just hot condensate from the steam main, dropping into the wet return.Let me clarify. The heat spreads in this order: 1. Supply main (overhead) 2. Supply drop 3. Wet return (ground level). All of those are connected as shown in the picture above. The dry return main and the drop from the dry return to the wet return are NOT hot. I.e., in the picture, the vertical drop on the left is hot, but the one on the right (partially hidden by plywood) is not. This tells me that the heat in the wet return is coming directly from the supply, not coming back from the radiators.
So the supply drop gets hot, at the floor the return drop gets hot ( How far up ? If it's exerting pressure it's height should be no higher than the boiler waterline ,,)
and what of the wet return at this time? Does it get hot before the return backfills ?
And we're assuming the wet return is getting hot from the return.. it's not coming from any other connection downline ... Right?
