Heat Master MF series

Simply Rad

I have a new project starting which I am install radiant floors with a Wood boiler and a LP boiler. The customer built a large shop last year and used a Heat Master MF 10,000 boiler. The unit was turned on this past January, so not a lot of use so far, thou he went through 25 cords of wood. I have no knowledge or experience with Heat Master, though I have installed other Biomass boilers. Does anyone one have input on the product and manufacturer? Thanks Jeffrey

GroundUp

I'll bet a dollar to a Dolly Madison donut his underground piping is full of water and/or uninsulated. Where are you located? How big is the shop? Are these full cord or face cord? What kind of wood? How is the shop insulated? What type of underground line is buried? What type of emitters are in the shop? I install quite a few of those units including one at my own home, and 25 cord would last me 3- 4 years in MN heating 5200 sq ft and DHW. With some more info, I'd be happy to share what I know. Are you adding a house to the loop or what is your scope on this project?

EYoder

I install HeatMaster wood boilers for a living and am glad to answer any questions or help any way I can too.
25 cords would be a lot of wood for a typical house heating load.
However we had an MF10,000e heating a large shop here in VA that went through at least that many cords. Two 2,000 CFM air handlers running non stop pulling cold air through, 25' ceilings, 12,000 sq. ft. only 3/8" insulation, several big doors with lifts going in and out... You get the picture.
They built another shop so it totaled 24,000 sq ft and switched to a B series automated chip boiler.
My point with all that ramble is that the shops can be a surprising heat load, greenhouses can be also.

hot_rod

If it is a non gasifier, that probably runs around 40- 45% efficiency. IF you burn dry red oak? With soft, or green wood probably in the 30%. Burning battle kill pine perhaps?

If you know the wood species you can look up the BTU per cord, compare that at 40% efficiency and see how it matches the building load.

A good read in this NYSERDA doc.

hot_rod

Use the BTU content of the wood times the burn efficiency

EYoder

> @hot rod said:
> If it is a non gasifier, that probably runs around 40- 45% efficiency.

Yes, the MF is a regular updraft, GS or G series are much higher efficiency gassers.

Simply Rad

Ground up... I had my first meeting with the builder and site manager yesterday. We talked about alot of things but in conversation he said they had burned 25 cords. The shop 8000 ft2 was built last year, well insulated and is slab on grade radiant. The problem is the wood. I live in a ski town in colorado with lots of aspen and beetle kill pine, aspen burns hot but fast. The unit is about 50 away from shop and uses 2 pre-insulated line sets, but only buried 3' deep.

The owner is building a 8000ft2 house he wants heated first with the Heat Master and 2nd with an LP boiler. The house will have slab below grade radiant floor and Warmboard on the main and second levels. I am alittle concerned with the low mass of the MF unit(180-230 gallons), as I have installed 800 gallon buffer tanks with Biomass systems. The home has a design load of 160,000 btus(lots of glass).

Anyways I was most concerned about the manufacturer and it seems Ground UP and EYoder like the company and the products.

EYoder

FYI, the MF10e will put out a maximum of 500,000 btu/hr albeit with a 4-5 hour burn time. 8 hour burn rate is about half that.
The 10,000 in the model # is a rough estimate of maximum well insulated sq footage.
You might be pushing it's limits.

Simply Rad

EYoder. Can we chat? 970-846-2445
Thanks Jeffrey

GroundUp

@Simply Rad did you happen to see what type and size of pre-insulated line set is buried? They make a wrap style in a corrugated drain tile type jacket which is very prone to water infiltration, and they make a closed cell foamed type in a heavy plastic jacket. Water infiltration will dump GOBS of heat in the ground. 8000sq ft, hopefully the underground is 1-1/4" minimum to carry the load and keep return temps to the boiler up? I installed a Central Boiler of similar size to the MF10 last fall to heat a 7200 sq ft shop, all slab on grade radiant as well, but the Central dealer sold the HO 1" line claiming "I do it all the time" despite my repeated pleas to upsize. I had to run a PL-55 circ and build a mixing manifold at the stove to bring return temps above 100 degrees, and at anything below 15 degrees outside, that stove would never catch up. It ran constantly for almost 6 weeks straight during a cold snap and never came up to temp once. 3ft bury is of no problem with decent line, I never bury deeper than 2 ft unless for another reason. We often leave it sit above grade if the install happens in winter and snow will sit right on it. As Yoder said, the limits of that stove are already being pushed with a shop of that size which I assume has fairly tall sidewalls? Buffer tank or not, I don't think there will be enough firebox to keep that stove going for more than 2-3 hours at a time on a design day with soft wood. He may want to swap to an MF20 or C800 after adding another 8,000 sq ft of load IMO.

Simply Rad

Thanks for replay Ground Up. I spoke with Heat Master tech support today and was very surprised on the lack of tech data on the unit. I am a hydronic's guy and flow/pressure drop are critical for any system design. Tech had no info on that. he also said I would only need 5-10 GPM flow rate through the unit which seems very low to me, creating a very large delta T therefore creating a low return temp. I also ask about some type of bypass(Termavor valve) to protect the unit from condensating and he didn't recommend one. He also recommended I use 1" lines for S/R? As for the existing shop I just saw PEX (no O2 barrier) on the pipe and no name though it did have a corregated jacket? What flows would you recommend for the unit. Then I can size my S/R lines appropriately. This might be a good application for a delta T pump. Very the speed of the pump, depending on the amount of heat, to maintain a close delta T.

So now I want you to understand the existing MF10000 is for the shop only. The owner wants another unit for the new home. The house load is 160,000 BTUs at design conditions. Again, I want to make sure the unit is of sound quality and the company provides good customer support. As I am finding out the existing unit was not installed properly and I will probably have to fix that system also. As for a buffer tank, I think it will help for shoulder seasons and also help raise the low temp radiant return temps, which will raise the return temps to the MF unit. Radiant supply temps are between 70-115F depending on outdoor reset. I will use a mixing valve on the radiant supply.
Thanks for reply

GroundUp

Did you tell him the house was 8000 sq ft before he told you to use 1" lines? Flow rate depends on the heat load for the building. The lines will carry roughly 10k btu per GPM right? 160k heat loss for the house means 16 GPM at a 20 degree DT which cannot be accomplished with 1" PEX at atmospheric pressure. 1-1/4" like Rehau or 32mm like Logstor holds a true 1" ID like copper would, and I've found it to carry about 12 GPM topside VS 7 GPM topside for 1" (<7/8" ID). A heat load like you're looking at, I would recommend looking at the Thermopex 1-1/4" sold by Central Boiler dealers. It's expensive, but is a true 1-1/4" ID and will carry 16 GPM at atmospheric pressure. Don't need barrier pex for the OWB because they are atmospheric. Delta T pumps in factory form are not big enough to move that volume of water (that I've seen) so one would have to get fancy with controls. Typically the OWB are constant circulation anyway, so I don't see the benefit to a DT anyhow as payback will take forever. I don't know what flow rate HM wants to see with that stove, but I can't imagine it needs more than 6-8 GPM. If mixing gets poor in the tank (which should never happen using 1-1/4" Thermopex) a guy can add a shunt/mixing pump on the stove to keep things mixed. I really don't see any benefit to a buffer unless he plans on batch firing. Letting the stove idle does nothing but dump BTU out the stack, they like to run constantly if anything. The MF7 or C375 holds 180 gallons and would provide a nice platform for the 160k load of the house. As for the return temps from the floor, they ought to be near irrelevant. As you are a hydronics guy, I assume you will be closing and pressurizing the floor loop with a plate exchanger separate from the OWB loop and not pouring dirty oxygen infested water into the floor loops? As long as you can maintain the flow through the OWB loop across the plate, return temps will never be harmful to the stove. Termovar or TV of sorts are not necessary if you do all the other homework and build a proper system. They are only to assist a crappy install otherwise.

hot_rod

If it is the MF 1000, their info shows approx 500,000 BTU/ hr output. Call it 40% efficient with a good burn and quality wood, so 200,000 BTU/hr. What about an altitude de-rate since it is basically an atmospheric burner? 3% for every 1000' above 1000' elevation is commonly used, call it 7000' in your area? So another 18% derate.

So maybe 164,000 BTU/hr output is more realistic? You need to move 16.4 gpm if you run a 20°∆, to move that output. You could play around with the ∆ and get that gpm down, but it really needs at least 1-1/4 pex. Or a super sized circ Figure the head with all the piping and HX in the loop.

Doesn't really matter what the building needs or wants the bottleneck will be what the units actually capable of providing. I certainly would not size the distribution around their 500K estimated output.

Any prolonged return below around 140F will creosote up that monster, and the passage way look like they would be tough to clean out when it creosotes up.

I've worked on some Taylor brands with a tubular HX and a jack hammer was needed to de-creasote those puppies.
They need return temperature above the dew point of the fuel, wood dew point is a bit trickier to pin down, the moisture content of the wood has a lot to do with it

Any/ all boilers will condense when return temperature is below the dew point. Granted a sloopy heat exchanger design can handle cold return for a period, I'd get it above condensing operation within 10- 15 minutes.

In Europe, which is still a huge wood boiler market, all the boiler return valves are pre-set at 140F. You are wise to address return protection, even a simple aqua stat to cycle off the cir until it catches up, that is common on many wood boilers. But you do need to also worry about freeze protection.

EYoder

> @Simply Rad said:
> EYoder. Can we chat? 970-846-2445
> Thanks Jeffrey

Yes, I'll try to call tomorrow.

I wouldn't worry too much about sticking to a 20F delta T, the return dumps into the middle of 150+ gallons of water above the firebox and won't condense flue gases. Needs at least 5 gpm to prevent stratification.

EYoder

> @hot rod said:
> If it is the MF 1000, their info shows approx 500,000 BTU/ hr output. Call it 40% efficient with a good burn and quality wood, so 200,000 BTU/hr. What about an altitude de-rate since it is basically an atmospheric burner? 3% for every 1000' above 1000' elevation is commonly used, call it 7000' in your area? So another 18% derate.
>
> So maybe 164,000 BTU/hr output is more realistic? You need to move 16.4 gpm if you run a 20°∆, to move that output. You could play around with the ∆ and get that gpm down, but it really needs at least 1-1/4 pex. Or a super sized circ Figure the head with all the piping and HX in the loop.
>
> Doesn't really matter what the building needs or wants the bottleneck will be what the units actually capable of providing. I certainly would not size the distribution around their 500K estimated output.
>
> Any prolonged return below around 140F will creosote up that monster, and the passage way look like they would be tough to clean out when it creosotes up.
>
> I've worked on some Taylor brands with a tubular HX and a jack hammer was needed to de-creasote those puppies.
> They need return temperature above the dew point of the fuel, wood dew point is a bit trickier to pin down, the moisture content of the wood has a lot to do with it
>
> Any/ all boilers will condense when return temperature is below the dew point. Granted a sloopy heat exchanger design can handle cold return for a period, I'd get it above condensing operation within 10- 15 minutes.
>
> In Europe, which is still a huge wood boiler market, all the boiler return valves are pre-set at 140F. You are wise to address return protection, even a simple aqua stat to cycle off the cir until it catches up, that is common on many wood boilers. But you do need to also worry about freeze protection.

The btu rating is maximum output, not input. An MF10 put out 400,000+ BTUs for several hours, obviously consuming fuel at an amazing rate.
It's a beast of a boiler.

hot_rod

The btu rating is maximum output, not input. An MF10 put out 400,000+ BTUs for several hours, obviously consuming fuel at an amazing rate.
It's a beast of a boiler.

Good to know that, thanks.

Would you derate for efficiency and also altitude at that Colorado location?

EYoder

I've never seen info on how altitude affects wood burners. I'd like to know.
Everything around here (SW VA) is between 1,000 - 3,000 ft so I've never looked into it. Nowhere near Colorado.