Boiler only heating one zone

[CMo82]

I have a Burnham hydronics series 2 boiler and it’s only heating the finished basement zone and not the upstairs zone.

It started by only heating the front rooms of the house upstairs and now it is heating none of them.

The Taco zone box shows there’s a call for heat. And I hear the pipes moving water and vibrating behind the baseboards, but the water in them is clearly not being heated.

Thoughts?

 

[Dana]

You may have too much air in the plumbing on the zones that are not heating. Even if it's getting some flow through the section with the air it's clearly not enough. If you're lucky there will be air bleeders under the end of one or several baseboards on the disfunctional zone for letting the air out. A typical bleeder valve looks roughly like a 5/8" hex nut with a screwdriver slot in the top and tiny hole on one side:

The screwdriver slot is actually a needle valve- turning it counterclockwise will open it up, letting air & water out of the system. If it just piddles a steady stream of water, no hissing or chugging of air mixed with the water, turn it clockwise to stop the flow and move on to the next one.

Is it more than 1 story above the basement? If yes, what is the vertical distance from the boiler to the highest baseboard on the system?

There has to be at least 12-15 psi of system pressure measured at or near the basement boiler when no pumps are running for 1-2 story systems. If for some reason the system pressure is running low it could be pulling air into the system at the upper levels of the system. If that's what is going on water needs to be added to the system. Most systems have an auto-fill pressure reducing valve for filling the system from the potable plumbing, and there is usually a valve between the auto-fill and potable plumbing for isolating the system completely from the potable water. To add water to the system and raise the pressure the isolating valve needs to be open.

 

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[CMo82]

I tried bleeding them all and a few let out a little air hiss, none of the hissing was major, and none let out water.

It’s a small (about 1000 sq ft) one floor house with a basement. The basement has its own zone because the previous owner created a room down there.

How do I check the psi? How would I add water to the system?

 

[Dana]

If none let out water, the system pressure is low, or a valve is closed or something.

IIRC if you lift the front panel off the Series 2 Burnhams there will be a pressure & temperature gauge on the same panel as the boiler controls.

To add water to the system, find the auto-fill, which may be sticking, or isolated by the shut off valve. It'll look something like this:

The valve labeled " manual fill valve" is actually an auto-fill with a lever on the top for manually opening the valve. If the shut off is all the way open the auto-fill should automatically add water to the preset pressure (adjustable with screwdriver on the exterior.) Sometimes they get sticky, but toggling the manual lever a few times usually frees it up for another year (or 10.) Whether the auto fill is working automatically or not you should be able to add water to the system manually with the lever (if it has one.) For those without a manual lever turning the adjustment screw a full turn in either direction will usually free it up, but be sure to not adjust the pressure over or under the 12 psi range.

If the expansion tank is shot it could be contributing to the problem too, but you'd probably have noticed the pressure relief valve dumping system water at the end of a burn.

 

[CMo82]

If none let out water, the system pressure is low, or a valve is closed or something.

IIRC if you lift the front panel off the Series 2 Burnhams there will be a pressure & temperature gauge on the same panel as the boiler controls.

To add water to the system, find the auto-fill, which may be sticking, or isolated by the shut off valve. It'll look something like this:

The valve labeled " manual fill valve" is actually an auto-fill with a lever on the top for manually opening the valve. If the shut off is all the way open the auto-fill should automatically add water to the preset pressure (adjustable with screwdriver on the exterior.) Sometimes they get sticky, but toggling the manual lever a few times usually frees it up for another year (or 10.) Whether the auto fill is working automatically or not you should be able to add water to the system manually with the lever (if it has one.) For those without a manual lever turning the adjustment screw a full turn in either direction will usually free it up, but be sure to not adjust the pressure over or under the 12 psi range.

If the expansion tank is shot it could be contributing to the problem too, but you'd probably have noticed the pressure relief valve dumping system water at the end of a burn.

P

 

[CMo82]

Psi is reading 0, temperature is reading 80

 

[Jadnashua]

Two things:
- if the safety circuits are working in the boiler, it shouldn't try to turn on the burner if the pressure is too low. A typical minimum is around 10-12psi, and about 14 or so isn't uncommon, depending on how high the highest point is in the heating circuit, you may need more.
- if you don't get water out of the bleed valves, you'll never get the pump to move water through the loop...so, you need to fill the system so the pressure is higher, then it should be able to purge the air and then start to circulate the hot water (since, raising the pressure, should allow the burner to turn on).

 

[Dana]

No big puddles of water?

At 0 psi the boiler will usually make sizzling and banging noises when firing up. Is that happening?

The system CLEARLY needs more water in order to function correctly!

Before you fill the system find the expansion tank. Most are bladder-types with a Schrader valve on one end (same as a car or bike tire.) Tap the side of the half with the air valve- it should "ding". The side connected to the plumbing is full of water (or should be) and won't ring. If both sides are dead, push the air valve to see if it releases only air, not water. Then pump it up to 15 psi or so.

Turn off the power to the system ( or turn the thermostats off). Find the fill valves and pressurize the system to 15psi, then go up and release are at the baseboards until just water comes out before firing up the system. If you're lucky that should be enough to establish sufficient flow to heat the place.

 

[CMo82]

I fiddled a little and the heat is on.... should I leave it be?? Or should I bleed the baseboards and try to figure out where the problem originated?

 

[Dana]

Bleeding the baseboards is worthwhile if there isn't sufficient flow for them to heat. If they're all running hot, the system's venting system should purge the air in the system automatically.

Keep an eye on the system pressure. If it keeps losing pressure there is a leak somewhere. There is some chance that the boiler is leaking to the fire-side of the boiler plates but only when they are hot, carrying away the lost water up the flue. Eventually those leaks get bigger.

How old is the boiler? I think Burnham stamps a manufacturing date on the nameplate that has the BTU-in, BTU out information etc, which is also inside the front cover hatch near the pressure & temperature meter. If there it no date, it's most likely encoded in the serial number. Yours is probably a Series 2 P202 (?) or perhaps (for no good reason) a P203. Hopefully it's not any bigger than 3-plates! If the thing is old enough to have been around during the first Clinton administration it's worth at least starting to think about a replacement. As a first cut for sizing, run a fuel use heat load calculation. A 1000' apartment would have a heat load of about half the output of a P202, or less, and it may be worth looking at either heating the place with a condensing boiler or a condensing water heater. It takes a bit more analysis to figure out the optimal solution, including the amount of baseboard per zone, etc..

 

[CMo82]

I don’t know about the age, but it’s a series 2.

It’s making a bit of a rattling noise in the pipe immediately after the circulator.... but the heat is still working.

 

[Dana]

The pump may be cavitating a bit or there's a bit of air in the mix. As long as the pressure stays in the 12-15 psi range when the boiler is at idle and not above 25 psi when firing it should continue to work, at least for the time being.

Series 2 Burhams have been around for something like 30 years or more. The older ones had a standing pilot ignition and were rated 78% AFUE, with an 80% steady state combustion efficiency. The newer ones are all 82-83%, with no standing pilot (the ignitions have varied a bit.) If the DOE BTU / INPUT BTU ratio on the nameplate is only 80% it's likely to be more than 10 years old, if it has a standing pilot it's likely to be over 20 years. But look for the date or coding in the serial number. At some point they're not worth fixing (or keeping.)

See if you can figure out where the water went. If it's not leaking or spitting out of the vent the leaking boil plate theory becomes more likely. If it's not leaking badly you can probably finish this heating season with it, and replace it before it becomes an emergency swap-out in the middle of a cold snap. MassSave currently has very generous cash rebate subsidies for swapping out gas fired cast iron boilers for something more efficient when the boiler is 30 years old or older.

 

[CMo82]

Thanks for all your help!

 

[Dana]

I'm glad you got it going- it's pretty cold tonight!