my oil boiler is a brunham ras series(couldn't find exact model). it provides both heat, and hot water. it's about 20 or so years old. possibly a little older.

 

 anyway.........no heat. hot water's fine. i tried bleeding the radiators, and got quite a bit of air out of a couple of them. the thing won't fire up though with the

thermostat set above ambient. when i run hot water, it runs perfectly. went down in the basement, felt pipes, most feel hot, 'cept one going to one of the living room

radiators that i'm getting only air out of. went back down in the basement to look things over. the guage shows me 170F for water temp, but zero for pressure. i can't tell if the

pump motor is running or not, and don't have a dvom at home to test it with.

 

 anyone got any clues before i hafta call service out?

My guess would be a frozen pipe somewhere near an exterior wall. The fact that you lost pressure during the coldest night in a year can't be just a coincidence!

I'm going to assume you have hot water radiators, not steam. I know nothing about steam systems.

 

Do you have an expansion tank and a pressure gauge? Is there a permanent feed of mains water into the system or do you have a shut off valve for adding more water?

It sounds like it could be that you have lost some water out of the heating circuit somewhere, but if you can bleed the radiators there must be some pressure still - is there pressure to expel air from the highest radiator in the house? Losing water could be a burst pipe, but I would doubt that if you have pressure remaining to bleed air out. It is more likely a slow loss of water over time.

It is possible the bladder in the expansion tank has failed. If so you can squeak by temporarily by feeding water in to build pressure, bleed the radiators some, feed more water, etc. Just be careful to leave the pressure at the lower end of the scale with the system cold when you're done with the process. Then schedule getting the pressure tank replaced ASAP.

2 hours ago, 1LtCAP said:

pump motor is running or not, and don't have a dvom at home to test it with.

You should at least feel some vibration if it's running.

Do you have multiple zone valves, if the LR pipe feels cold? Maybe a bad one? Some zone valves have a bypass switch, and you can open it up to get some hot water to circulate by convection. You can also test to see if a zone valve has power by putting a screw driver at the top of the coil and see if there is a magnetic pull when energized.

yes. hot water radiators. the 2 on the front porch are still the old school cast iron radiators. the rest in the house are more modern and more "efficient". to be honest, they suck.

 

i think there's an expansion tank hanging from the cieling. it looks like it's about 5 gallons. and it wasn't feeling hot. i don't see any way to add water to it.

 i don't think there's zones in this system. even though the boiler is only 20'ish years old, the rest of the system is stupid simple looking. tstat turns on the boiler, hot water flows to all the radiators. now that i'm thinking of it, i'll hafta check the radiators when i take a shower, see if they get hot or not.

3 minutes ago, 1LtCAP said:

i think there's an expansion tank hanging from the cieling. it looks like it's about 5 gallons. and it wasn't feeling hot. i don't see any way to add water to it.

The expansion tank will just be connected to the radiator circuit. The place to refill the system will be nearby, most likely, but not directly into the tank.

update.....just got up again(sick.....finally caught a nasty cold along with a "pipe smack in the back of the head" kinda headache) and since the wood stove went low, the heater was running. went downstairs, showing around 12-15psi and still 170 temp. i touched the tank, it's not hot at all.......

52 minutes ago, 1LtCAP said:

the heater was running. went downstairs, showing around 12-15psi and still 170 temp. i touched the tank, it's not hot at all.......

So the burner runs when the t-stat calls for heat or hot water and temp/pressure are ok. 

Doesn't sound like the expansion tank, a failed expansion tank will cause excessive high pressure, 12-15 psi is normal. 

First thing I'd check is if the circulator pump runs when there is a call for heat.   

2 hours ago, Bomber said:

So the burner runs when the t-stat calls for heat or hot water and temp/pressure are ok. 

Doesn't sound like the expansion tank, a failed expansion tank will cause excessive high pressure, 12-15 psi is normal. 

First thing I'd check is if the circulator pump runs when there is a call for heat.   

i was trying to feel if it was spinning...i feel "something" whenever the boiler's running.

 

 but....the initial post was that i had no heat/no boiler activation when the tstat was turned up, but the boiler would fire up to give me hot water. now it's still heating the house........i'm wondering if johnnyb nailed it with a frozen pipe somewhere around the perimeter.....and if so, i am thankful it didn't burst

2 hours ago, 1LtCAP said:

i was trying to feel if it was spinning...i feel "something" whenever the boiler's running.

 

That why I like my big Taco Red Baron circulator pumps.

If the house is quiet I can hear/feel them switch on and run even from the second floor.

2 hours ago, 1LtCAP said:

.i'm wondering if johnnyb nailed it with a frozen pipe somewhere around the perimeter.

No doubt! It's the only logical conclusion given the circumstances! Watch for leaks when they thaw!

@DeerSlayer may be able to help but he's been running around all last night with no heat issues.

Sounds to me like your circulation pump is going or gone. PM me with a phone number, if you would like some tips. I do this for a living

@1LtCAP You use a piece of hose as a stethoscope to find the source of engine noises. You can use the same method on the pump motor too see if it's running!

If you have hot water, the circulation pump is probably ok.. 

First thing to check is the relay switch for the zone. They do go bad. You should hear it actuate when the zone goes on. The hot water zone is working.. . So it stands to reason to check this first. That relay controls basically everything to turn the heat on/off.

As some some mentioned there is a small metal tab you can flip to turn the zone on manually. If the heat goes on, you know to replace it. 

I have a similar Burnham set up that's from 2006 and has had a few parts replaced over the years and works like new. 

Even with a frozen pipe the furnace should fire up, and the pump should turn on. Furnace will turn off when it hits temp, and you should hear the pump remain on. They are quite, but you can still feel and hear them a little.