Anyone know about gas boilers for radiator heat?

Gas fired boilers are not adjustable. Oil fired ones are, based on what nozzle you use. Either way, the boiler shouldn't make more heat than you can use. They have a high limit and shut off when they reach that temp. Temp will slowly drop if nothing calls for heat, and it will fire up back up when it hits its low limit or when a zone calls for heat. If his bill is too high, something else must be going on. The heat the boiler is generating must be going somewhere other than just heating the house. I've seen uninsulated pipes in crawl spaces and buried in slabs waste crazy amounts of heat. Also seen boilers where the internals get covered with crap and more of the heat goes up the chimney than goes into heating the water. Check can stick open allowing convection and steady heat loss. Lots of things can go wrong. He should have a heat guy look at it. If its old, replace it. The new high efficiency stuff is great.

Typically boilers, especially older boilers, are oversized so they end up "short cycling" which is inefficient, but if fuel was cheap when it was installed it didn't matter if it had extra capacity and burned a bit more fuel than needed.

A little more information would be helpful.

• how old is the boiler?

• does it use a pilot?

• how does he heat his hot water?

As already stated unless it's a newer high efficiency it's not going to have a lot of adjustability. The newer ones will modulate the firing to go from a low percentage (10-30) up to 100% based on outdoor temp and if it's heat or hot water calling for it to fire.

I'd recommend checking the system for air. If it has air trapped in the radiators it's not going to transfer heat efficiently and run longer than needed.

Other options would be to see if an "outdoor reset" can be added. It will replace the single target temp hydrostat with unit that will adjust the boiler target temp based on outdoor conditions. Whether or not this is an option will depend on the boiler and how he heats domestic hot water.

i have the EXACT system. i also have the exact same story, $400 per month gas bills from nov to mar. this year i shut it off. we are running a 5KW heat strip in the attic AC unit, controlled by a seperate thermostat. even if my power bill goes from the usual $80 to $280, thats still better than $400 (+$80 for power).

but, were it my house (its a rental), what i would do is remove the stupid radiators. all of them. remove all the cast iron piping too. then run insulated piping from the heater to the attic, and put an aluminum radiator or intercooler from summit behind the blower fan. let the boilers temp control do its thing, though id probably need to modulate the BTUs down to keep from short cycling, might even need to drop the high/low set points to keep the temps inside the attic A/C unit down under 160 degrees. then, just let the heat side of a nice digital thermostat run the blower fan when it calls for heat. this way all the heat from the boiler goes into my house, not my basement, walls, floors, crawlspace, etc. as an added bonus, i would be able to modulate the heat load in rooms im not using, as opposed to now where the rooms i dont use are about 110 degrees, and my living room is 56...

-J0N

The radiators themselves, especially if they are base board types, have they ever been cleaned? If they are loaded up with dust and hair and other things, the air can't move through them and transfer the heat. Which means the boiler keeps firing (up to it's control limits), but the house isn't getting heated.

Here in the midwest I've never heard that hot-water heat was cheap. In fact, we looked at a house years ago and passed because it had that kind of system(it was even a newer system). One of our friends knew a previous owner, and we got firsthand accounts of how bad the heat bills were.

That bit the latest service tech said about BTU burner capacity. Did your son have the unit serviced prior to the gas bill becoming very high? For there seems to be a terribly mismatched application of burners, which would have lots of heat and money going up the chimney.

As mentioned, gas burners are not adjustable, per se. Though you can replace the orifice, and therefore change the gas flow and btu capacity. There's a big mismatch between 40,000 and 130,000. If the unit is indeed being overcharged with gas, a huge amount of heat and money are going up the chimney and not into the water. This is something to check, and the internet makes it easy enough to do. Just look up the numbers on the burner nozzles.

I'm a little concerned about the servicing he got this last time as well. As mentioned, there is no adjustment per se on a gas burner. So what the service man did to reduce it from 130,000 to 90,000 I do not know. Though since the tech gave very specific numbers, I rather suspect he used some smaller nozzles that he had. Go further, and get smaller still. You'll have to adjust air flow to balance the system. Also check on the boiler to make sure it really is 40,000. That sounds very small for a residential heater. Normally, they are up around the 100,000 range.

Don't you blow tubes at noon everyday?

Sorry, that's all I got.

It sounds like there is some confusion regarding the numbers given by the tech.

The boiler rating is probably at 90,000 BTU with the changes the tech made. But because of its age and design it is probably only 50% efficient so it is burning 180k btu to produce 90k btu.

The 40,000 is probably the technicians educated guess at the heat load. Unless he took measurements of the house, windows, insulation, etc and adjusted for local conditions it is only a guess.

I suspect the issues leading to high heating bills are the poor efficiency of the boiler and the use of hot water radiators instead of baseboard.

In automotive terms the hot water radiators are the equivalent of a heater core with the fins removed. They have much lower surface area to transfer heat.

Add to that the localized room heating from the radiators compared to a length of baseboard running along all the outside walls creates uneven heating and more short cycling as the room temp evens out and the thermostat calls for heat again.

My ex's house had a 50+ year old boiler when she bought her house. IIRC, she was seeing bills similar to yours until she bit the bullet and bought a new boiler (a System 3000). While I can't really recommend that brand (she's had tons of issues with reliability over the years), it did reduce her gas bill considerably when it's working correctly. It also has a heat-exchanger for the domestic hot water, so one benefit is it gets continual use/exercise throughout the year (compared to my forced air oil burner, which sits dormant for 8 months)

petegossett wrote: Here in the midwest I've *never* heard that hot-water heat was cheap. In fact, we looked at a house years ago and passed because it had that kind of system(it was even a newer system). One of our friends knew a previous owner, and we got firsthand accounts of how bad the heat bills were.

It is E36 M3loads cheaper than LP forced air or electric....plus the house stays warm for about a day after losing electricity in the winter.

I grew up in Fuel Oil/LP boiler homes with the giant cast iron radiators.....now I live in one with forced central air and electric baseboards. Every winter I miss the radiators. Warmer house on a lower thermostat setting and I already pay at least 2x of what my parents do each winter, and my house is better insulated.

I have baseboard radiators and a water boiler that dates to the original build of the house.

The only time that the boiler became inefficient was when it needed cleaning and set off the CO monitor. I find it a very cost effective way to heat the house.

What they don't tell you about the new high efficiency units are that they are not designed to live long enough to recoup their cost; this from the guy who could have sold me a new high efficiency unit.

Call Richard Trethewey with This Old House.

We have an old 2700 sq ft house with hot water heat and a 30 year old boiler. Our gas bill is around 75$ per month in the winter.

I would check for air in the radiators first. Bleed them from the highest rad first down through the house. Don't forget about any in the attic.

Then I would check for a "full" expansion tank or whatever the hell it is called. (the tank usually hung above the boiler that is supposed to have some water in it, but not be full - drain some water from the tank if it is full).

Then I would make sure the water supply line works properly. There should be an automatic valve for the supply line and usually a shut off valve as well. Make sure the shutoff valve is open and manually open the automatic valve and see if you can hear / feel water running through the line. If the water does go through the line, leave teh shutoff open and let the automatic valve do its thing.

3 more bits of info....

1) there should be a pressure gauge on your unit. IIRC, you should be about 13 psi (+/- 2 psi) for the system to be operating properly. (look this up to make sure). If it is not in that range, you either have water or air where you shouldn't.

2) You can adjust individual flow to radiators by that big hand valve on the radiator. This can be used to balance heat throughout the structure. Room too hot, close the valve a bit.

3) There is usually a small motor that forces the water through the system. It is usually located near the boiler. Make sure that little motor is running and pushing water. If it is not, all of your heat is going to stay near the boiler (natural convection is only going to work so well).

Hope this helps!

Edit: Check out this link: http://homerepair.about.com/od/heatingcoolingrepair/ss/trblsht_boiler_4.htm

Rob R.

+1 on checking the expansion tank. That failed on the ex's system and it caused all sorts of headaches. The most obvious one was water getting spit out the pressure relief valve. Which then stopped sealing and had to be replaced.

Ian, I'll agree with a water logged expansion tank creating headaches, but that would be with regards to water leaks and such, wouldn't it? Not high fuel consumption bills. Unless it was a special catastrophic failure that was dumping water and being constantly refilled with cold supply side water. But I don't think that's the case here. Is there something I'm missing?

In reply to foxtrapper:

Not sure - it was causing the system to cycle a lot and not really put out any heat. I don't remember if it was affecting the amount of gas used.

Some of the things I listed may not deal directly with high gas consumption. However, if the system has air or water in the wrong places it is not going to work properly and can cause all sorts of issues.

If the system was losing that much water you would probably know it. Listen to the water inlet pressure reducing valve, if there's that bad of a leak anywhere in the system to sky rocket the bill the PRV would cycle way too often.

I could see changing the orifice size to increase/ reduce capacity somewhat but not from 90K to 40K, my guesstimate would be maybe 10%. I'd stick w/ the original orifice size and troubleshoot from there.

Definitely bleed the rads but if that doesn't help I'd look at the pump like Rob said. Even if the motor runs, a broken coupling (if equipped) won't circulate, prolly be noisy too. The system could still work but by gravity circulation. I could see that causing higher gas usage, the burner will fire less often but fire more times before the t-stat set point is met.