Mascot wood boiler-water not hot

[Bill H]

I have a Mascot wood boiler that I have been using the last several seasons. It was installed in 1981 and I have been in this house for the past nine years. I have had no complaints about the system until this week. I have no trouble getting a good hot fire, but the water struggles to get over 140 degrees. Even if the water is not circulating it struggles to rise. I don't recall the appearance of the firebox when the unit was working; it now has a hard black glaze over all of the surfaces. The heat does not seem to be conducting through it. Any ideas? Let me know what other information you may need. The oil furnace works fine to heat the house but I would rather continue to burn the wood.

Thank you,

Bill H.

 

[Eric Johnson]

Hi Bill. Welcome to the Boiler Room.

I have a couple of questions:

How dry is your wood compared to years past when it worked fine?

Do you have a damper on your system and if so, do you leave it open all the time?

Is there a baffle in the boiler?

Do you get a lot of smoke from your chimney?

Are you burning less wood now than in the past?

A boiler is a pretty simple machine. If there's a hot fire in the firebox, there's very few places for the heat to go--specifically, it can go up the stack or into the water jacket.

 

[Bill H]

Hi Bill. Welcome to the Boiler Room.

I have a couple of questions:

How dry is your wood compared to years past when it worked fine?
I burn mostly scrap lumber (poplar, mahogany, oak, maple). The wood is dry.

Do you have a damper on your system and if so, do you leave it open all the time?
The damper in the pipe is always open. The draft is always open as well since the water will not get hot enough to close it.

Is there a baffle in the boiler?
Yes.

Do you get a lot of smoke from your chimney?
Little to no smoke. In fact I have trouble with the flue temp being too high.

Are you burning less wood now than in the past?
More. The heat does not seem to be transferring to the water jacket.

A boiler is a pretty simple machine. If there’s a hot fire in the firebox, there’s very few places for the heat to go--specifically, it can go up the stack or into the water jacket.

 

[Eric Johnson]

If your flue temps are high, then it sounds like most of your heat is going up the stack. I'd check the baffle and make sure that it's in the correct position, and I'd also play around with the damper to see if you can bring down the flue temp without getting smoke backing up into the house. Sounds like a baffle problem to me. Hopefully somebody else will check in with more ideas.

 

[webbie]

FYI, we are getting a lot of posts like this in the Pellet forum - low heat or less heat than before.

I suspect that much of this is due to the VERY cold snap we have just experienced. Such cold and wind can double the normal November heat load of a house.

Another thing is that once the water gets below a certain temp it can become a self-fufilling prophecy - trying to raise cold water to a hot temperature creates lot of problems. Boilers are designed to only raise the temp a relatively small amount each time the water passes through.

I don't know about your hookup, but I would consider adding a 4-way mixing valve or some other sort of return hookup so that you can balance the amount of heat going to the house and keep the boiler at temperature. It may be that you have to use some of your backup fuel (oil), but the bottom line is that you have to keep the water hot - hopefully over 160.

 

[mpilihp]

do you have a thermometer on your flue pipe, whats the temp going out to the chimney?

Any smoking issues if you open the door while its burning?

Do you hear a roar when you do open the door?

If the stack temp is over 700, and you hear a roaring sound even when not opening your door, then sounds like an issue with the baffle and your loosing alot of heat up your chimney.

If temps are low and your getting smoke when you open your door to the boiler then you have a bad draft problem. Possible something obstructing your chimmney? When was it last cleaned??

 

[Bill H]

Maybe that this the answer. I will raise the temp that the boiler circulator kicks on. I had it set low. I will put it at 140 and set the draft to close at 180. I don't know what the capacity of the boiler is but it sounds like I may be letting the water circulate at too low a temperature. I have been fooling with the settings. I start a fire this evening with the new settings and see how it goes.

Thank you very much for the input.

Bill

 

[Bill H]

Added info:

Yes the stack temp gets over 700 and its hot! inside. The door can get quite hot. The baffle has only one position or it falls down. I only get a puff of smoke when I open the door if the fire is cold. I had the chimney cleaned at the end of last season. I do get a roar from time to time. I have a heat exchanger on the stack and it runs often. The basement gets hot. As I said my last post I will reset the temps and evaluate what happens.

Thanks,

Bill

 

[mpilihp]

I have an old style wood boiler, non gassifier and I have my aqustat set to circulate water when its at 180 and it stops at about 160, runs for a short time then stops, lets the water heat up and runs again. I have my draft set to shut down at 185 and my overtemp aqustat is set for 210 deg. If you have baseboard heat you will want to let the water get really hot before having the circulator kick on.

~ Phil

 

[Bill H]

Thank you to all who responded. I have set my aquastat to what Phil recommended and it seems to be working well. I have been watching the temp gauge and it does not seem to correlate to the aquastat. I don't know if the either the aquastat is wrong or the temp gauge is wrong. Perhaps the temp gauge lags behind the actual circulating temp.

Thanks again,

Bill H.

 

[jebatty]

Does your boiler have fire tubes or water tubes or water jacket? One reasons for decline in heat output of a boiler is buildup of ash or creosote on the water-fire heat exchanger mechanism. If fire tubes (hot burning exhaust gases pass through tubes surrounded by water), brushing the inside of the tubes to remove buildup can help a lot. If water tubes or water jacket, removing ash-creosote buildup on the fire areas making contact with water will do the same. In m boiler (fire tube), a good cleaning can reduce flue temp by over 100F.

 

[mpilihp]

Yeah my aqustat temp doesnt corolate to the temp gauge on the output of my boiler and the temp gauge of the boiler. THose two match so I go with them. Set the aqustat to whatever makes it turn on at 180 and off at 160, you could make it turn off at a lower temp, I have mine stop at 160 so the temp in my indirect DHW tank will be at 160 at least.

~ Phil