Forum newbie questions regarding my boiler

[Robmac]

I have a few questions and I hope some of you can provide me with some feedback. I always have a professional work on the furnace - I'd just like to know what is going on.

Background:
I have a 18 year old residential boiler, with hot water baseboards. Domestic hot water is via a built in coil. Honeywell controller with adjustable high, low and diff temps.

The water from the faucets can get really hot this time of year so I normally drop down to see what the furnace is running at. (once about four years ago it came out boiling initially so I turn it down to 175 - 155 with a 15 diff. This seem to have fixed the problem. (It was 190, 160 and diff set to 20). We do not have a cold water mix valve for domestic hot water.

Here's what the furnace it is currently running at.

With a domestic hot water demand call the water temp on the furnace gauge will climb to about 180 and then the furnace cuts off. (We have, and continue to have plenty of hot water).

A call for heat will cause the furnace to run until the temp reaches about 210, this seems high with the controller's high temp set at 175, is this normal? I would expect a little variation as nothing is exact, and perhaps some parasitic heating after the burner goes out but 35 degrees seems much doesn't it?

Also I've just notice that the pressure is currently at 25lbs (180 degrees) and it tops out right at 30lbs when it hits 210f. It looks like the pressure relief valve had activated some time in the past, don't know when.

Five years ago we replaced the fresh water pressure valve and also the pressure relief valve so I'm surprised that the relatively new fresh water valve would be gone since it is only a few years old.

I'm thinking that I need either another fresh water proportioning valve or expansion tank, and that controller is going bad, or the problem could lie in the thermocoupler?

Your thoughts and feedback guys?

thanks in advance you any help and Merry Christmas everyone.

Robert

[hearthman]

Rob shut it down until you can get a pro in there to set it up properly without blowing up your house!

Those temps. and pressures are way too high.

Your potable hot water should not be over ~135F. Above that, you can scald somebody. The recommendation is actually about 125F. If you have a controller (and you should) this should be a simple setting. As for the boiler, you shouldn't normally be heating water over ~165F and most homes only need about 12-15psi. You should have an automatic feed valve/ pressure reducer/ strainer w/ a bypass function. Have the strainer cleaned at annual service and have the tech set the pressure to where your upper rads get the hot water they need but no more. Make sure you have a reliable air removal system such as a Spirovent and your expansion tank is not water logged. If a diaphragm tank, have the tech make sure the diaphragm is not ruptured and the pressure matches the boiler pressure.

You boiler may have been overfired and damaged.

Terminology: a 'boiler' makes hot water while a 'furnace' heats and distributes air.
Hearthman

[Roscoe]

Robert

First a furnace heats air and a boiler heats water, stop messing with the aquastat, get it serviced and get a mixing valve or an indirect water heater, get rid of that dinosaur of a instantaneous hot water coil .........;)

[Robmac]

I have not been messing with the aquastat, I adjusted once four years ago.

Of course I'm going to get someone professional in to look it over I was just wondering what you experts thought that it might be off the top of your head.

Do you think it's the aquastat going bad or the thermocoupler?

We've live in the house for nine years and not one of the kids have ever been scalded, but I centainly agree that the current setup for domestic hot water is not great.

[beenthere]

The aquastat may be bad.

Have it checked.
And also have a mixing/tempering valve installed for your domestic hot water.

[heaterman]

Kind of a time bomb you have going there Rob. Temps and pressures are to high so you need to call the service tech ASAP. While the system is being repaired, have a mixing valve installed for the domestic hot water.

[Robmac]

Thanks guys...

I called a professional and described what's going on, he thinks it's the aquastat as well.

They are going to drop over on Monday to repair it.

I'm going to leave the domestic for now because we are budgeting to replace this boiler next summer. It will be 19 years old by then and it is a side wall power vent, (which I hate). We're going to replace it with a side wall sealed unit that does not draw any air from inside the house. My next door neighbor just put one in this fall. I really like having hot water on demand with the in coil design, but I will be putting in a mixing valve.

[Wolfbyt]

If I understand your question correctly you are having a problem with high domestic hot water temperature when your boiler is calling for the burner to come on and the boiler water temp is over 200 deg. and you are getting your hot water from a coil inside your boiler. If so, you need to make sure you have a tempering valve installed on domestic hot water exiting the boiler set for 120 deg F. This valve adds cold water to keep the water to your faucets set at a constant temp of 120 deg F regardless of the temp your boiler is putting out unless the temp of the boiler drops below 120. Make sure your installer follows the manufacturers installation instructions. These valves require a heat trap and if you have faucets which use over 2.5 gpm you may need to have a flow restrictor installed. This will take care of the domestic hot water side. Although some aquastats do go bad I have not run across many. If you pull the aquastat out check the probe there should be heat transfer grease on the probe to get a good transfer from the well to the probe.
Please have a qualified person look at this.

[beenthere]

Consider getting an indirect water heater.
Then you don't have to maintain boiler temp 24/7.
Plus, you can use outdoor reset to save even more on your oil bill.

[hotwaterworld]

Turn your boiler off for couple hours and note where your pressure is at after 2 or 3 hrs. If pressure drops off down to say 20 or so, it is not your auto fill valve causing problem. You may have lost charge in your expansion tank if it is a diaphragm type or it is water logged if standard expansion tank. When tech comes, make sure they disconnect diaphragm tank from system to test pressure other wise your just seeing the system pressure and it is not accurate. Depending on how tall your house is determines how much pressure you should have. If basement and 2 floors above, then appx 12 to 16 psi depending on if piping is overhead attic piping and feeding down or just from floor up to radiators. 16 appx would be for overhead piping. This should also be what your fill valve is set to when system is cold, not when its hot and running. After all this, then pressure should only rise maybe 4 or 5psi when heating up. Re: temps, system for baseboard probably does need to run at 180 during colder temps outside and even some need to go near 200 if amount of radiators is nominal when real cold out. Ps, and yes, you definately should have thermostat mix valve on domestic hot water. Good luck.
After reading again, your pump could also be malfunctioning, and then heat not being removed from boiler so burner does not shut off as fast when no flow ocurring and then overshoots due to built up heat in cast iron. Or still could be aquastat. Good luck again.

[Robmac]

At 160f pressure is roughly 25lbs, it approaches 34 - 35lbs at 210f.
My expansion tank is mostly empty, bottom couple of inches slightly warm though. (Yes the valve to it is open).

The boiler cycles normally (low end) for domestic, (it obeys the controller, but seems to permit over temp by about 35f-40f. I'm thinking that it might be a probe issue or perhaps a bad aquastat.

Circulation seems fine, both zones, house is split entry.

Once I have her obeying the controller completely again we'll troubleshoot the pressure issue.

My buddy is coming over to fix it Monday morning... he is a professional... owns his own company.

Gotta love winter!!
thanks,
Rob


Turn your boiler off for couple hours and note where your pressure is at after 2 or 3 hrs. If pressure drops off down to say 20 or so, it is not your auto fill valve causing problem. You may have lost charge in your expansion tank if it is a diaphragm type or it is water logged if standard expansion tank. When tech comes, make sure they disconnect diaphragm tank from system to test pressure other wise your just seeing the system pressure and it is not accurate. Depending on how tall your house is determines how much pressure you should have. If basement and 2 floors above, then appx 12 to 16 psi depending on if piping is overhead attic piping and feeding down or just from floor up to radiators. 16 appx would be for overhead piping. This should also be what your fill valve is set to when system is cold, not when its hot and running. After all this, then pressure should only rise maybe 4 or 5psi when heating up. Re: temps, system for baseboard probably does need to run at 180 during colder temps outside and even some need to go near 200 if amount of radiators is nominal when real cold out. Ps, and yes, you definately should have thermostat mix valve on domestic hot water. Good luck.
After reading again, your pump could also be malfunctioning, and then heat not being removed from boiler so burner does not shut off as fast when no flow ocurring and then overshoots due to built up heat in cast iron. Or still could be aquastat. Good luck again.

[Robmac]

Update.

I had my buddy (who runs his own heating company) come over the other day and look at my boiler. He replaced my Honeywell aquastat with a used unit and reduced the pressure to 15 lbs.

He looked over my install and suggested that a New Yorker boiler would be a good replacement for my 19 year old unit. It sounds good to me so this is what we going to have him install next summer.

Also it turned out that my 5 year old fresh water valve to slowly letting extra water seep through which is what was driving my pressures up. Since we're replacing everything in six months I simply reduced the pressure back down to 15lbs again and closed the fresh water feed. I've been keeping a close eye on it for the past four days and the pressure has always matched my baseline measurement. Since the boiler resides in our laundry room checking the pressure every few days doesn't take but 5 secs.

thanks guys.
Robert