Heatmaster MFe 5000 - temp regulating

EasternPromise

New Member
Oct 26, 2020
8
Ontario
Hi folks,

I've inherited a Heatmaster MF 5000 unit and am giving it a go this winter. I'm burning well seasoned/stacked wood; same as I would use in my woodstove.

I'm having trouble with regulating a reasonable temperature. I'm set at 170 degrees with a 15 degree variance. Whenever I load up for a longer burn - i.e.: overnight, or first thing in the AM - the boiler routinely burns too hot (over 200 degrees), steams over resulting in water loss. Not only should this not happen, but it will be increasingly difficult for me to refill water given the winter freeze.

I've gone over the trouble shooting guide for overheating boiler here: https://dealers.heatmasterss.com/wp-content/uploads/2020/06/1.1-C-MF-TroubleShooting-Guide.pdf

If the furnace overheats: 1. Check that all doors are closing properly and that door gasket is completely sealing. 2. Check that the solenoid damper plate is opening and closing without hang-ups. 3. Check venting and fan box on rear of furnace for air leaks. 4. Check that the temperature settings are correct. The furnace should be set on Heating Mode (H1) and the high temperature setting should be set to no higher than 185 F. 5. Check chimney draft. If the chimney has been extended too far or has a strong wind blowing over it, it may cause a draft down the furnace. 6. Check water level. 7. Make sure the door and ash drawer are air tight. 8. Check to ensure all pumps in the system are running.
None of the above conditions are present and I'm still having issues with furnace burning hot and overboiling.

Any suggestions?

Thanks a lot.
 

Eureka

Feeling the Heat
Feb 4, 2018
339
NW Wisconsin
Hi folks,

I've inherited a Heatmaster MF 5000 unit and am giving it a go this winter. I'm burning well seasoned/stacked wood; same as I would use in my woodstove.

I'm having trouble with regulating a reasonable temperature. I'm set at 170 degrees with a 15 degree variance. Whenever I load up for a longer burn - i.e.: overnight, or first thing in the AM - the boiler routinely burns too hot (over 200 degrees), steams over resulting in water loss. Not only should this not happen, but it will be increasingly difficult for me to refill water given the winter freeze.

I've gone over the trouble shooting guide for overheating boiler here: https://dealers.heatmasterss.com/wp-content/uploads/2020/06/1.1-C-MF-TroubleShooting-Guide.pdf

If the furnace overheats: 1. Check that all doors are closing properly and that door gasket is completely sealing. 2. Check that the solenoid damper plate is opening and closing without hang-ups. 3. Check venting and fan box on rear of furnace for air leaks. 4. Check that the temperature settings are correct. The furnace should be set on Heating Mode (H1) and the high temperature setting should be set to no higher than 185 F. 5. Check chimney draft. If the chimney has been extended too far or has a strong wind blowing over it, it may cause a draft down the furnace. 6. Check water level. 7. Make sure the door and ash drawer are air tight. 8. Check to ensure all pumps in the system are running.
None of the above conditions are present and I'm still having issues with furnace burning hot and overboiling.

Any suggestions?

Thanks a lot.
So is it set for blower on at 155 / blower off at 170?
 

Eureka

Feeling the Heat
Feb 4, 2018
339
NW Wisconsin
I have basically the same model and know it well. 170 on 180 off is factory setting and I’ve tried it all but nothing works better for me. The wider your differential is, the more it will overshoot.
If it’s overshooting by 30 degrees, there is a leak somewhere.
Take off the blower fan and look into the air duct where the solenoid-controlled steel flapper lives to verify it seals after the blower shuts off. Ashes/coals can backfire and block it from closing. My fan and the entire duct filled up with coals and ashes last week because I forgot to empty the ash pan, and it backpuffed on a warm day.
 
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Eureka

Feeling the Heat
Feb 4, 2018
339
NW Wisconsin
Thanks. I will look into this. Is it possible that it overfires because I've been too, *ahem*, 'generous' with the fuel loads?
Absolutely. It will burn what you put in it; to an extent. That’s what I tell myself while loading.
 

Eureka

Feeling the Heat
Feb 4, 2018
339
NW Wisconsin
Thanks. With a proper full load (up to the line) - how many hours of burn are you getting?
It’s hard to answer this broadly because my heat loads are way over the rated capacity of my Heatmaster C150 (same as MF series), so I end up loading more often.
In general, long burn times mean wasted, smoldering wood while there is no heat being pulled by the house on warmer days, or when loads are satisfied.
My longest burn times are overnight, so about 12 hours, and it’s usually ready for wood by then; it’s empty and low water temp after very cold nights.
 
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Eureka

Feeling the Heat
Feb 4, 2018
339
NW Wisconsin
I’ll add that chasing very long burn times will end up leaving you disappointed I think. Heatmaster didn’t really design them that way. That is more of a Central Boiler selling point; fill it to the top and walk away until tomorrow while a cold barrel full of fresh cut wood smolders inside a gigantic tank of water.
I think you’ll like the Heatmaster after you get to know it though. I try to fill it no more than halfway for long away times, and a log or two on top of coals if I know the house won’t be drawing heat during the day. Keep the ash pan clean and the firebox scraped out and stirred up. Use water treatment and have it tested. Heatmaster offers lifetime water analysis and warranty if they test your water every year.
 
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brenndatomu

Minister of Fire
Aug 21, 2013
6,015
NE Ohio
I try to fill it no more than halfway for long away times
I've read of many people that have found out that partial loads end up saving a lot of wood...
 

Eureka

Feeling the Heat
Feb 4, 2018
339
NW Wisconsin
I've read of many people that have found out that partial loads end up saving a lot of wood...
Definitely. I just don’t think there’s room for proper combustion when the firebox is full. With appropriate loads of big, dry wood, the MF and C series really do burn cleanly for a conventional design. I’ve noticed that big splits and rounds work much better than smaller. But it’s gotta be dry. I have a thermocouple in the flue about 12” out of the top, and with the blower on and fire cruising, I might see 400-550 on a normal load. 700+ if it’s packed.
I realized at that point that the more wood I tried to stuff in it, the more I was sending out the chimney.
 
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E Yoder

Feeling the Heat
Jan 27, 2017
492
Floyd, VA
I was swamped with service calls and haven't checked in for a few.
Good advice, especially on the loading.
If it boils chronically it's sucking air somewhere. As was mentioned pull the fan and check the flap, if it's an older model where the flap lands on the fan intake make sure if lands tight. It only takes a small hole to overheat.
To check door gaskets I put some bark or chips in and run it hard til it smokes heavily, then put a board over the chimney til the smoke pushes back into the ashpan. Then turn fan back on and it'll push smoke out of the gaskets.
 

EasternPromise

New Member
Oct 26, 2020
8
Ontario
Thanks all.
I've reduced the loads downs and the issue appears to have resolved itself. But I'm also having to refill a lot more frequently to maintain temperature. When the boiler is running optimally, how often should it be refilled to maintain a steady 170-180 degree temp? I'm using a dry mix of softwood and hardwoods.
 

Eureka

Feeling the Heat
Feb 4, 2018
339
NW Wisconsin
Thanks all.
I've reduced the loads downs and the issue appears to have resolved itself. But I'm also having to refill a lot more frequently to maintain temperature. When the boiler is running optimally, how often should it be refilled to maintain a steady 170-180 degree temp? I'm using a dry mix of softwood and hardwoods.
Very generally, 2-3 times a day
 

maple1

Minister of Fire
Sep 15, 2011
10,691
Nova Scotia
Thanks all.
I've reduced the loads downs and the issue appears to have resolved itself. But I'm also having to refill a lot more frequently to maintain temperature. When the boiler is running optimally, how often should it be refilled to maintain a steady 170-180 degree temp? I'm using a dry mix of softwood and hardwoods.
Do you need that high a temp all the time to keep your house reasonably comfortable? Shouldn't hurt if it drops to even 150 before you reload. Different systems work differently though, and there's a lot more to a system than just the boiler. You dont want return water coming back to it that is less than 140 too often.
 

E Yoder

Feeling the Heat
Jan 27, 2017
492
Floyd, VA
I would guess if it drops to 150 it's out of wood and losing its coal bed. It's intended to cycle without running out of wood.
 

EasternPromise

New Member
Oct 26, 2020
8
Ontario
I may have had a leak from the ash drawer. I've cleaned it all out and unit has been performing significantly better since. No boilovers and far easier to regulate temps, even overnights.
Thanks all.
 

DickNitro

New Member
Dec 7, 2019
10
Southern Illinois
So I too have an old Heatmaster MF5000 just put in service this year, but I agree with the 170 on 180 off. My temps never get higher than 185 when its mild and lately (single digits to <0*F) it barely breaks 180. I work 12's with a 1 hr commute so at least 14+ hours between loads. I'm currently using some last summer seasoned pecan as well as maybe 6 week old fresh cut white oak. Ive mixed them, done only pecan and I've done only green white oak. The fire box has probably 3-4" of coals and 1-3 half burnt logs in it every time regardless after 14 hours. I'm heating 2600ft^2 right now. I love it and I'm borderline obsessed with it to be honest.

Eureka, Does the inlet damper on your fan rest on the heads of 2 screws, or does it seal completely? Mine is always maybe 1/4" open on one side and I've wondered about this alot.
 

Eureka

Feeling the Heat
Feb 4, 2018
339
NW Wisconsin
Eureka, Does the inlet damper on your fan rest on the heads of 2 screws, or does it seal completely? Mine is always maybe 1/4" open on one side and I've wondered about this alot.
The damper seals flat against the housing. It has a 1/4” hole drilled in it to allow some passive intake; I think this is a coal burning adaptation. I closed that hole off with silicone, and I noticed the upward water temp creep stopped.
 

E Yoder

Feeling the Heat
Jan 27, 2017
492
Floyd, VA
Those screws should be removed and the ring siliconed down to prevent air leakage.
It'll creep temp on a warm day a lot less.