A person named Nahsani recently posted the following on the alt.hvac
"My two-year old Slantfin Boiler won't heat the house above 65 degrees, and
it's usually at 60 degrees. It'll come on and off randomly for short
periods of time (as short as one second) and over a long period of time,
it may bring up the temp to 65. As another example, I had the (new)
thermostat, which my oil company replaced saying that was the problem, up
to 72 overnight and into the day, and the temp in the house is still 60
degrees. I have also left the thermostat pegged on high for two days with
the same result. The company who installed the boiler doesn't, for some
reason, believe that this problem exists, because when they came, the
house was "warm" i.e. 65 degrees! and the gauges on the boiler were up to
the correct pressure. I have obviously severed business relations with
them, but I still have the problem. Any ideas what might be causing this?"
And, he later wrote:
"My old boiler was ancient - 50 year old, big. Then it puffed back and
wrecked my house. Anyway, I only replaced the boiler and the pipes leading
into it. It used to work fine (the new one). Although my ex-boiler guy
insisted that the on and off operation is normal, I really think it's
important. I would say the btu rating is less for the new boiler, but I
don't know and I don't know what the old one was. I've lived here for 13
years and it is a tiny house - 810 sq.ft. one floor. Mostly new windows
and insulation. The whole house is cold and I have no idea about the
piping. The weird thing is that it got my house up to 70 yesterday, for
the first time in a long while. Today, it won't get going."
I decided to also post it here in case anyone here has and ideas or
On Thursday, January 15, 2015 at 11:16:42 AM UTC-5, TomR wrote:
Who knows. It doesn't make a lot of sense. If it's only coming on and
off for short periods of time, incapable of raising the temp, then that
should be demonstrable when the tech is there, regardless of whether the house
happens to be 65. Just raise the thermostat to 75. What happens?
If the thing is not coming on, not generating proper heat, it should be obvious. Something here doesn't compute. If the OP
has really given the contractor many attempts to fix this new install
and they can't or won't, then I'd call another HVAC company to solve it, then
sue the original company in small claims for what it costs, if necessary.
Any speculation here seems pointless, no indication the poster is DIY,
going to try to fix it himself. One of the easiest things, the thermostat
has already been replaced.
Some of it does seem to be hard to figure out, but one thing that I like in
the other alt.hvac thread about this is that the OP has been willing to post
back more info in response to questions etc., and that is helping to fill in
the picture some.
I re-posted it here because I thought that Stormin Normin and maybe others
here may have some ideas.
I was definitely wondering what may be causing the short cycling where his
heater keeps cuttin gout and then restarting before getting the radiators
hot. I don't know if a bad circulator pump could cause that or if something
else is being detected by a sensor of some type that keeps telling the
heater to stop and then re-start.
Few possible things.
There is a high limit switch that will cut the burner at a pre-set
temperature. That would make the boiler cycle more if it is set too low
or defective. If the circulator is not moving the water to the rest of
the house it will shut down the burner. If the boiler cycles for just a
couple of seconds, I'd first feelt he pipes and see if the water is
moving. If not, replace the pump. If yes, check the limit switches.
There are other potential problems but not enough information to
discuss. Since the boiler is 2 years old, I have to assume it worked OK
last year. If so, that removes speculation about the size of the
boiler. It is probably smaller in output, but that is because it is
more efficient. If the old boiler was 60% and dumping 40% up the stack,
an 85% boiler does not have to be as big.
All good points, IMO. In the alt.hvac group the OP did write back that his
"new" heating system did work last year and that the recent developments
where it kept short cycling and won't heat the house properly were new. So,
IMO, that ruled out the possibility that the heating system was undersized
for the house (which he says is small -- 810 sq. ft.), or that the piping
system was designed incorrectly (it's the same piping system that the old
Is the thermostat actually calling for heat all this
time? Can you see on the display?
Do the radiators get hot at any point during the day,
or only a trace of heat?
Is there a circulating pump on the system?
Christopher A. Young
learn more about Jesus
If the boiler is starting up, getting hot, and shutting off before the house gets warm, one likely cause would be something is stopping the hot boiler water from getting to the radiators.
It could be as simple as an air lock. Or, a bad pump somewhere. Or, bad controller for that pump.
If that were the case, I would expect the thermostat to keep calling for heat, and the boiler to be maintaining its setpoint, whatever that is, and coming on and off just enough to keep the boiler water from getting cold.
I think we pretty much narrowed it down to that. What we don't know is
what was actually checked. You can feel the pipes around the house to
see if they are hot. Most systems will allow some gravity circulation,
but not enough to heat the house properly. Depending on the pump, you
may see, hear, or feel the motor running
Assuming it is ok, the high limit switch would be my next step.
On Saturday, January 17, 2015 at 3:20:32 PM UTC-5, Ed Pawlowski wrote:
I'm not seeing why you suspect the high limit switch. Wouldn't that require hitting the reset, if tripped? This boiler short cycles during the day without tripping any safeties.
The old boiler was 50 years old. The boiler was replaced but not any of the pipes or radiators, so they are all 50 years old. They might have worked fine the first year then a chunk of something came loose and there's a blockage somewhere.
The high limit switch shuts the heat off when the boiler water is at
temperature. If it cuts it prematurely, it won't heat the water enough
to heat the house. No reset required, that is how it is supposed to
work to make the burner cycle.
The water cools as it gives its heat to the rest of the hose. Once it
get down to the low limit, the burner is started again.
Possible, unlikely. Check the flow as I suggested.
Then you check for circulation. Water has to be moved to distribute the
heat. I said before that gravity will move some of the water, but not
enough to properly heat the house. The circulator may be working a bit,
but not turning fast enough to do the job.
Yes, apparently Nahsani has "left the building".
Sorry for wasting everyone's time on this one. I decided to try posting
this here on alt.home.repair to help Nahsani. And, I only did so because he
was responsive in the alt.hvac group where he originally posted his
question, and he posted about 5 follow-up posts there in response to
questions and feedback that he received on that forum. If it were not for
his willingness to follow up on the discussion there on alt.hvac, I would
not have posted his question here. However, after I posted his inquiry
here, and I also followed up further on alt.hvac, Nahsani stopped following
up on the alt.hvac forum or here.
But, I do think that all of your thoughts and suggestions were probably
right on the money based on what he described as heater symptoms.
Did he ever say he woudl read AHR? He reads through
FlashNewsgroups.com, I think, and maybe it's hard to read this group.
Oh, look at this:
The Flash NewsGroups WebSite is temporarily DOWN for maintenance.
Sorry for any inconvenience, we should be back up in 2-3 hours.
Thu Feb 17 17:15:24 PST 2011
This site is down, but no need for alarm
You were right, it wasn't you.. it was us.
But we're different now, and we really want to change.
Give us another chance, and before tomorrow we'll be a whole new site, a
better site, promise.
Service should be restored before the end of January 10th
We apologize for any inconvenience.
If you use 18.104.22.168 instead of flashnewsgroups.com, stop. That
address will not work after today.
He posted from Jan. 10 to Jan 15, so it must have come up and then gone
When I entered flashnewsgroups.com, I got "server not found, but when I
entered wwww.flashnewsgroups.com, I got what is above. Normlally FF
inserts the www. ????
Well, it looks like flashnewsgroups is back up. But, it also looks like
people have to pay money to use it and to access newsgroups.
I'd recommend just getting a local heating engineer to come and take a look
at it really, after all they'll be able to diagnose the fault and fix it p
retty fast usually.
The last time I had a problem with my boiler, I was going to use BG but wit
h the call out fee's they mentioned I thought "no chance". I was wondering
what to do, then I heard a radio advert for some firm called STL Heating -
"well, what the heck" I thought, these guys are local - why not ?
So I gave them a call and thankfully the call out fee was a lot less so I'v
e been using them ever since for my boiler service.
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