Outside Air Too Cold?

retiredmt

I've got a three year old Lochinvar boiler (Model WHB155N) and when it gets extremely cold outside (-10 F and below), the boiler will either be struggling to keep up for heat or even go into lockout. The first year it was fine but the successive two years there has been issues. I live in the mountains in Montana at 8000 feet (if that helps). Any ideas what could be happening? Lochinvar suggested disconnecting the outdoor sensor next time and see if that helps. Opinions?

EdTheHeaterMan

Maintenance... Maintenance... Maintenance.

The first year it was fine but

Have you looked at the condition of the flame sensor? Now that it is 3 years old, the sensor may have some build up on it that is reducing the flame signal. Compound that with extra cold combustion air and the flame signal may not be strong enough from time to time. There may also be other maintenance items that can contribute to flame failure lockout. The manual will have the recommended Maintenance items to look for.

Also does your boiler fall under this recall? https://resources.whmaas.com/images/boiler-recall/Lochinvar-Safety-Notice.pdf. This is probably not the reason for your problem, but if you have this problem, then you might as well get it corrected. WHB155 is on the list. Check your serial number

hot_rod

Is it on outdoor reset control? Could be it needs to be boosted up a bit. What error does it display when it locks out?
Intake air vent clear? Is it a high altitude model, if so they work fine at 8000, even 10 and 12,000.

A cleaning and burner check with an analyzer will tell about the life it has lived. They are what they breathe.

retiredmt

Thanks for the quick responses. In March of '22, burner was cleaned. Also gas valve, both computer boards, fan motor, ignitor cable, air pressure switch, spark ignitor were replaced between March and May of this year. I want to emphasize that this boiler is working perfectly and was until we got the -35 F last week. At that point, the boiler never locked out, but was struggling to provide enough heat, thus the house was getting cold. Fortunately I have 2 large gas fireplaces and 2 heat pumps to supplement in an emergency. As soon as it started to warm up outside to about -10, the boiler started working properly. And yes the recall was taken care of. Again thanks to all for the help.

EdTheHeaterMan

So no error codes or lock out... Then you have something that is too small. It could be the boiler, It could be a section of pipe, It could be the way the radiators are installed, It could be you don't have enough radiators. The phrase that comes to mind is. Your chain is only as strong as the weakest link.

1. Have you had a heat loss completed on your building? this is a calculation that determines what size heater you need on the design temperature day (what I used to call the coldest day of the year).
This will let us know if your heater is big enough.
2. Is the heater large enough to heat your home on the design temperature day
3. If yes... Are there enough radiators to heat the home on the design temperature day?
4. If yes... Are the radiators installed is such a way that heat can enter the room efficiently?
5. If yes... Are the pipes big enough to get the heat from the heater to the radiators?

You may have answered YES to every one of these questions except one. That NO answer is your weakest link, and that means your SYSYEM can only get you 80° warmer than the outside temperature. So when you got to -35° outside, the SYSTEM could only get you to 45° inside because 45° is 80° hotter than -35°

The next question is, In the last three years, Has the temperature dropped below -35° before this past week?

The question after that: Have you experienced -35° outdoor temperatures with the previous heater? Was the previous heater able to maintain comfort during those low temps?

retiredmt

EdTheHeaterMan said:

So no error codes or lock out... Then you have something that is too small. It could be the boiler, It could be a section of pipe, It could be the way the radiators are installed, It could be you don't have enough radiators. The phrase that comes to mind is. Your chain is only as strong as the weakest link.

1. Have you had a heat loss completed on your building? this is a calculation that determines what size heater you need on the design temperature day (what I used to call the coldest day of the year).
This will let us know if your heater is big enough.
2. Is the heater large enough to heat your home on the design temperature day
3. If yes... The are there enough radiators to heat the home on the design temperature day?
4. Are the radiators installed is such a way that heat can enter the room efficiently?
5. If yes... Are the pipes big enough to get the heat from the heater to the radiators?

You may have answered YES to every one of these questions except one. That no answer is your weakest link and that means your SYSYEM can only get you 80° warmer than the outside temperature. So when you got to -35° outside, the SYSTEM could only get you to 45° inside because 45° is 80° hotter than -35°

The next question is, In the last three years, Has the temperature dropped below -20° before now?

Sorry I forgot to mention that the whole house is radiant (including the garage). And yes, in the first year we had almost a week of minus 20 and there were no problems. I was wondering if it's possible the exhaust and intake are too close (although according to Lochinvar they are alright). I was thinking of posting a picture of the two (it will have to be tomorrow).

EdTheHeaterMan

Did you experience -35° in the last 3 years before last week?

I have a story about the pipes being too small on a new boiler install.
https://forum.heatinghelp.com/discussion/comment/1705970#Comment_1705970
The system was old and worked fine for 40+ years with the old boiler until the boiler failed. The replacement boiler was more than adequate. The connecting pipe was too small to get ALL the heat from the boiler to the radiators. So when ever the temperature dropped below +21° outside, the boiler cycled by the high limit, while the circulator ran constantly because the thermostat never satisfied. The small pipe was the weakest link.

That is followed by a story about another customer who has a restriction in the baseboard radiators created by Wall to Wall carpet. The Carpet was installed so it was blocking the bottom inlet of baseboard radiators. As long as the outside temperature was above +20° outside, the "SYSTEM" was fine. The heater was big enough to go colder, the radiators were enough to go colder, the pipes were big enough to go colder, The carpet blocked the airflow so the radiator could not do their job... The weakest link.

EdTheHeaterMan

Is the entire system 3 years old? or just the boiler?

retiredmt

EdTheHeaterMan said:

Is the entire system 3 years old? or just the boiler?

The whole system. House was finished and we moved in 2019.

retiredmt

I was wondering if the intake absorbs a small amount of exhaust, can that have an affect on the performance of the boiler? I'm not talking about enough to cause a lock out, but enough to cause an issue.

STEVEusaPA

How's your gas pressure when you have this problem?

JakeCK

What's the design temp for that region?

retiredmt

STEVEusaPA said:

How's your gas pressure when you have this problem?

Not sure. I know that our gas fireplaces work fine. Do you know if there is a way to tell the pressure on this unit itself?

retiredmt

JakeCK said:

What's the design temp for that region?

According to Lochinvar this unit is designed to handle these temperatures without any issues.

hot_rod

What happens often with radiant floors is it works perfectly on paper. Then the home is built,
furnishings get moved into the space, cabinets, floor coverings, beds, dressers, etc. Anything that covers the "radiant panel" limits output. It's called heat flux, divide those covered areas into the actual room square footage to get the number.

So usually that comes into play at design or below design temperature conditions, where the system falls behind.

On those cold, or windy days, If the boiler runs non stop, it may be a bit undersized. If it cycles off and falls behind, the problem is distribution side. Either piping or heat emitters.

JakeCK

retiredmt said:

JakeCK said:

What's the design temp for that region?

According to Lochinvar this unit is designed to handle these temperatures without any issues.

Full disclosure I'm not an expert so defer to those here who are, I'm just a homeowner with an interest in this kind of thing.

That said, you misunderstand the relationship between design temperature and boiler output. Yes the boiler is designed to operate in those conditions. But that is only a small part of the story. That boiler can only output x number of btu's an hour. If the heat loss of the house is greater than the output of the boiler/radiation the temperature in the house will fall. You said you had no errors or lock outs. Assuming the boiler is working correctly, and modulating correctly you should be getting the rated output. If the temperature of the house is still falling that means you don't have enough boiler or if the system is cycling/modulating down you don't have enough radiation. Now if it hasn't received the proper PM and it is not delivering the rated output that could be the issue.

As hot rod stated adding furnishings such as carpet or area rugs to a house with radiant floors can cause a problem. Basically you are insulating your radiators. The system must respond by increasing the supply temperature to get the same output from the floors, however with a mod-con boiler that operates on outdoor reset it is setting the swt(supply water temperature) based on the heating curve. Now what I do not know since I haven't really played around with a modcon is if they will adjust the heating curve on it's own if it continues to get a call for heat?

JohnNY

I don't know if anyone's still doing this but for a little while there I was being advised by two different manufacturers' reps to install a PVC sanitary/cleanout tee on the combustion air inlet pipe of my mod-cons. Those are the tees that use a removable threaded plug on the bull. Leaving the bull open seems to solve some problems. I'll leave it at that.

HVACNUT

I don't have the science or any formula to back it up... but I believe combustion air temperature can effect burner performance. On Christmas eve, we had that cold snap on Long Island. I had one oil fired boiler in a closet with a 24 x 24 vent in the exterior wall for combustion air, and the homeowners left the boiler room door open so it got quite chilly in there. The house is unoccupied and they set the thermostats to 55°.
Riello F5 in safety on arrival. It would only fire if I partially covered the air inlet on the burner. I checked oil pressure, vacuum, and draft and all were good. 2 pipe oil lines. And I was the last tech to service the burner. I had a hard time getting ignition and a 0 smoke. I thought I had everything dialed in nice. I let the system run for 15 minutes then shut down the burner only. 10 minutes later I started the burner and had to cover the air again. I down fired it and did some T&E, and finally got it to recycle without my assistance. 
And I closed the boiler room door when I left.

JakeCK

I've heard intake air temp can affect performance too. But the op said later that it never locked out or gave any errors.

flat_twin

The outdoor reset programming may not be programmed for -35. If it's set for max supply water temps at -20 then that's all you get and the house will struggle to stay warm at temps colder than that. Do you happen to have the ODR programming parameters?

retiredmt

OP Here. Thanks for everyone's comments and suggestions. All make sense, but there is one last piece of info that might help. When the temperature of the house was going down, all zones were calling for heat (as they were supposed to). And the system's flame percentage never went over 35%, which means it wasn't even going into high fire mode. And the incoming and outgoing water temperature was only 95 degrees F. If anyone here is familiar with Lochinvar, does this info help?

JakeCK

Would need to know what the parameters are set to and some info on the build of your house would help too. Square footage, type of construction, etc. You said this is a new house so we can only assume it is well insulated?

95f sounds plenty hot for a radiant floor. Did you ever get any temperature readings on the actual floor it's self? You also mentioned the supply and return water temps were the same? That might be your issue.