Hardy H4 Issues

[tjmortenson]

Hi,
I have a hardy h4 that I installed last March to heat my 3000 Sq ft farmhouse, and it seemed to work fine then. This year I am burning 1 year seasoned split oak, and it struggles to stay up to temp. I have the aquastat set to 175, and the blower runs almost constantly. The blower is working, the blower door and solenoid working as well. Chimney is clean, and firebox is free of creosete. In the last 6 days it has burned a full cord of wood. Any ideas? Maybe it's just too small for my application?

 

[andym]

Hi,
I have a hardy h4 that I installed last March to heat my 3000 Sq ft farmhouse, and it seemed to work fine then. This year I am burning 1 year seasoned split oak, and it struggles to stay up to temp. I have the aquastat set to 175, and the blower runs almost constantly. The blower is working, the blower door and solenoid working as well. Chimney is clean, and firebox is free of creosete. In the last 6 days it has burned a full cord of wood. Any ideas? Maybe it's just too small for my application?

Have you checked the temperature of the water after it makes the underground trip to the house? A degree or two loss per 100 ft is acceptable. More than 5 or 10 degrees is not. If you have waterlogged insulation on those lines it will kill your efficiency. I don't know too much about boilers, but know this can be a problem in some situations.
Also, what exactly is the moisture content of your wood? (To some people 'seasoned' means stacked in the sun, to others it means a sprinkling of salt and pepper!)

 

[tjmortenson]

My water temp going into the furnace is about 1 degree less than at the boiler, I only have 30ft of line from the boiler to my furnace. Moisture content is 25 to 30 percent, could be better but I would think it's dry enough for a boiler.

 

[brenndatomu]

Where does the supply line go...HX in a forced air furnace? Or radiant tubes, etc?

 

[maple1]

My first guess is wood too wet.

 

[brenndatomu]

Moisture content is 25 to 30 percent, c

Tested how, exactly?

 

[tjmortenson]

I use a heat exchanger in my forced air furnace plenum. I test the moisture content by taking several pieces of wood and splitting them again, then test the freshly split side with my moisture meter. I'm just guessing that is the correct way?

 

[brenndatomu]

I use a heat exchanger in my forced air furnace plenum.

Is the thermostat calling for heat (making the furnace blower, and I assume a pump too) a lot, or for an unusually long time?
In other words, is it heating your home well, just using a lot of wood?
If so, I agree with Maple1...one year CSS oak is notorious for burning/heating poorly...what were you burning after you installed it last March?

 

[brenndatomu]

I test the moisture content by taking several pieces of wood and splitting them again, then test the freshly split side with my moisture meter. I'm just guessing that is the correct way?

Sounds about right...just FYI, the meters are calibrated to test the wood at about room temp too...not sure how much difference it makes as long as the wood isn't below 32*...and the pins need to be parallel with the grain too...I believe it will test falsely low if going across the grain.

 

[tjmortenson]

Is the thermostat calling for heat (making the furnace blower, and I assume a pump too) a lot, or for an unusually long time?
In other words, is it heating your home well, just using a lot of wood?
If so, I agree with Maple1...one year CSS oak is notorious for burning/heating poorly...what were you burning after you installed it last March?

My house is pretty big, 3500sq ft plus the 700sq ft basement, and it was built in the 1950s so it isn't insulated the best. Thermostat calls for heat for about 20 minutes at a time, every 20 to 30 minutes. I averaged 400 to 500 gallons of propane a month to heat the place before getting the boiler. I'm starting to think I may just need a bigger boiler.

 

[maple1]

I don't think a bigger boiler will fix burning 1 cord of wood in 6 days this time of year.

 

[brenndatomu]

I'm starting to think I may just need a bigger boiler.

But you said it worked fine in the springtime...was it warmer out then?

 

[E Yoder]

Hardy is one of the least efficient outdoor boilers so it's going to use more wood than some. Not meant as criticism, just saying it's super basic unit, chimney right out the top.
I'm assuming the water is coming up to temp? Make sure the air tube below the draft fan isn't clogged with ash. If it can't get air it'll smoke a lot and struggle to get up to temp.

 

[3fordasho]

My house is pretty big, 3500sq ft plus the 700sq ft basement, and it was built in the 1950s so it isn't insulated the best. Thermostat calls for heat for about 20 minutes at a time, every 20 to 30 minutes. I averaged 400 to 500 gallons of propane a month to heat the place before getting the boiler. I'm starting to think I may just need a bigger boiler.

Assuming a 96% efficient LP furnace your heat load is an average 55,000 btu/hr based on 450 gallons LP per month.
If you had a 80% efficient LP furnace your heat lead is an average 45,750 btu/hr based on 450 gallons LP per month.

A cord of sugar maple or red oak is roughly 24,000,000 btu assuming a moisture content of 20% or less. Your Hardy is 50% efficient on a good day and could be much worse depending on several things (wood moisture content being a big one) So taking 24M btu x 50% / 55k btu/hr=218 hrs = 9 days from a cord of wood.

A situation where you have higher moisture content wood or some other system in-efficiency (line loss etc) and your boiler system is only 35% efficient, then a cord of wood only last 6.3 days and if you don't have enough btu output capacity to meet that 55kbtu/hr load you indeed need a bigger boiler and did I say a lot more wood.

The best thing you could do is to reduce your heat load. I think my 3400 sq ft house in Southern MN has a heat load less than half of yours. A day like today with a low of 14F and a high around 30F my 1000 gallons of thermal storage will start at 176F after a batch burn and be down to 135F 24 hrs later. That is 341,650 BTU over 24 hrs to keep the house at 65-66F and standby losses in the boiler building (24x48') will keep that at 58F. So between the two that's only 14,235 btu /hr heat load.

 

[3fordasho]

Looking at the Hardy H4 specs I see Hardy rates it at 180k btu. Of course we all know how the marketing depts. have screwed up the btu output ratings and output ratings must be taken with a huge grain of salt.

So the Hardy H4 has a usable firebox capacity of 15-16 cubic feet. A pound of wood at 20% MC has 6734 btu available. A cubic foot of red oak is 45 lbs. So derating your firebox capacity about 1/3 to allow for air space between pieces you can stuff about 480 lbs of red oak into the Hardy.
480 lbs x 6734btu x 50% efficiency = 1.62 million btu available per burn or 67,340 btu average over a 24 hr period assuming loading once per day. That is at 50% efficiency. Drop that to 35% efficiency and you can see that you might have trouble meeting your 55kbtu/hr heat load because you are only going to get 47kbtu/hr at 35%.

Start using lower btu content wood per cubic foot and things get worse yet and add in the fact that the wood burning cycle is no where even output over that 24 hrs means the boiler is probably idling a bunch at the peak of the burn and then falling short later in the burn all of which does not help your overall efficiency.

You may have to load more than once per day but assuming you can stuff more wood through the hardy it should heat your house.

 

[StihlKicking]

Last year my hardy h2 was struggling just as you described yours. Everything was working that was supposed to be. That is except for my automatic fill valve. The float had deteriorated and fallen off. I didn’t know the water in my heater was low because the float valve also controls the indicator light on the side. My heater certainly didn’t know it was low of water. All it knew was that the thermostat kept calling for heat no matter how much wood it burned through.
FYI the heater wasn’t out of water completely. Probably about 25-30 gallons low would be my estimate. There was enough water that my temps measured correctly at the output and return but not enough to properly carry the heat load my house required. Also the heat from the vents was warm enough to keep the house somewhat comfortable but not the normal 150-160 degrees.

 

[tjmortenson]

Thanks for all the helpful information everyone. I think spending some money on air sealing, better insulation, etc on my house is what I need to do. Also started burning some whole logs instead of split wood and I'm getting closer to 12 hours burn time, which is awesome.