# Hardy H4 Wood Boiler Questions



## hondaracer2oo4 (Aug 21, 2011)

Hello again everyone, I am thinking of building my own OWB but have also found a Hardy H4 Boiler for a good deal. I was interested in anybodys experiences with them such as wood consumption, smoke, reliability etc. I will be heating a 2500 square foot old colonial in New hampshire build in 1795 with new windows and attic and basement insulted but not sure about walls yet. It will be a heat exchanger in the forced hot air system. The guy says that it needs a new patch on the back where it had been patched before. Is it common for these boilers to need patching? Where else should I look on the boiler for spots that could need metal help? Thanks alot!


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## dahmower (Aug 21, 2011)

How old is the unit? Does it have the.water saddles or ibeams in the bottom that the grates set on?
The saddle units have a bad habit for leaks on the saddles!!


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## Aaron441 (Aug 22, 2011)

I have a Hardy H25, which is the same design, just bigger. I love mine and would buy one again in a second. I have never had any trouble with leaks or anything else. I use a lot of wood, but I have a 3000+ square foot brick house with old windows and very little insulation. The smoke depends a lot on what I burn. If it is good dry seasoned wood it hardly smokes at all. If it is green wood, it can smoke a LOT depending on how green.
Having said all that, I would not buy the one you are looking at if it has been patched once and is leaking again. There are a bunch of Hardys near me, and I have never heard of one leaking and needing patched. I would wonder if someone overheated the hell out of that one or ran it dry or something like that. 
If you are determined to buy it, I would get a pro welder or boiler guy or something to look at it, and see what they think. It would also have to be really cheap. If you get on the Hardy website, they have a dealer finder on there. If there is a dealer in your area, they might have access to a used one in better shape than that. Good luck.


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## hondaracer2oo4 (Aug 22, 2011)

I am going to take a look at it tomorrow. Apparantly it had a pin hole leak around the return line to the boiler. The owner cut out a piece around that and replaced it. This spring it developed a leak around the output line in the same fashion the other side did. My brother in law is a professional welder so I think he can handle it. I will take a look and see what the deal is though. It is 500 bucks, I figure if it is decent than it is a good price.


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## Aaron441 (Aug 23, 2011)

That doesn't sound like too bad of a leak. I was thinking of a big crack somewhere. For $500 bucks, even if it is complete junk you could rip the pumps and controls off and scrap the rest and probably still make money.


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## hydro2 (Aug 24, 2011)

Yea for $500 I would buy it. I am going on 12 years with mine and no problems. I heat two homes. Mine is 3,300 sq feet including the basement and I heat my mom's house which is about 1,500 sq feet with no problem.


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## NC4AB (Aug 25, 2011)

The stainless steel in a H4 is probably worth $500.00 at the local scrap yard not counting the pumps and other stuff. 

Only issue to worry about is if the water used to fill it had a high chlorine content which can cause Stress Corrosion Cracks at the welds over time. (look for very fine spider web looking cracks).

I have a 1987 H2 that is still running strong and my FIL has a 1991 H2. Good Stoves from my experience.


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## hondaracer2oo4 (Aug 25, 2011)

Thank you for all of your responses. I did pick it up and I think that it is going to work out well. Apparently the bung plug for the aquastat started to leak around the weld. So the owner cut out a piece 6x6 around the whole bung and welded in a new piece of stainless with a new bung for the aquastat. Well when he welded he didnt have any stainless wire for the mig so he just used regular mild steel wire. Well the weld seam leaks. So my brother in law who is a welder got a new piece of stainless and is going to weld it in using stainless wire. Thanks again for all of your input.


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## indiansprings (Aug 25, 2011)

For 500.00 you can't go wrong, you can always scrap it and come out as previously mentioned. We sell wood to several people with Hardy's. IMHO they use more wood than a comparable CB or WoodMaster, we sell the guys with Hardy's a prolly 30-40 percent more wood than the CB customers in comparable size houses. They are tough units one customer heats 5k + sq feet of uninsulated shop and burns his wide open to keep up, he loads at 8am,11am,5pm and comes back at 11-12pm and loads, he will burn 5 to 7 cords a week, he is by far our #1 customer. It hasn't burned up yet.lol I think some of the models have fairly small water capacity, 100-125 gallon, one customer boils his over on a regular basis, he has it on a 4500 sq ft house and has a big family with all the showers and hot water use he also has to run his hotter than recommended to keep up. Used with design limits they are a nice little unit.


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## hondaracer2oo4 (Aug 28, 2011)

Thanks everyone. I am hooking up to a decent insulated 1795 colonial in New Hampshire that is 2500 sq. I bought it from a guy who was heating an uninsulated 5000 sq general store in NY. He said that he was going through 20-22 cord a year and loading it twice a day. His unit was about 75 feet from the store and the underground lines had no insulation on them at all. Just lines inside a 4 inch pipe. I am hoping to burn maybe 10-12 a year. 

He had his placed on a cement pad on the ground like most people do. I asked if about snow melt around the unit and he said that the ground in the winter is all thawed around the pad. So I was thinking that the cement is acting like a heat sink and sucking alot of the heat right out of the water in the unit. What do you guys think about putting two rows of cinder blocks down and bridging the gap between the two with 4x4s and placing the unit on top of that? I figured that the wood would be ok because the boiler temps should never get much over 180 because of the water. I would put some insulation underneath the 4x4s and the ground and then make a skirt that goes around that bottom so that the wind doesn't blow underneath and pull heat away.


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## Aaron441 (Aug 29, 2011)

I wonder how deep his lines were buried? The ground never thaws around my pad any quicker than anywhere else. Neither does my father in laws and he has the same unit. Our lines go four feet underground though. How cold does it really get there? Is the ground really freezing that solid anyway? A lot of times the ground will thaw around a pad or building first, even if there isn't a boiler on it.
Mine aren't terribly well insulated either, the lines are wrapped with a thin piece of foam insulation and then stuffed in a 4" conduit. But on a cold day when everything is working the lines are so hot in the house you don't want to touch them. It's over 100 feet from my house to the boiler.


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## hardy steve (Aug 29, 2011)

I bought my H2 second hand.I've been burning year round for three years.Mine was built in 87' as I was told by Hardy from my serial number.I had to replace auto filler solenoid and. Float switch.Before winter my door will be replaced.We love ours.


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## hondaracer2oo4 (Aug 30, 2011)

Thanks again for your replies. How about line size going into the house? I was thinking about running 1 1/4" pex. Other than price is there any disadvantages to running bigger lines? Will I get better heat transfer with the bigger lines? Havent decided if I am going to buy my own pre-made line or make my own. What do you guys have for lines and any numbers as far as heat loss from outside to inside? How about any snow melt? Thanks.


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## 1harlowr (Aug 30, 2011)

I have an H4. Only complaint is the door is a little small. If I remember correctly, the piping inside the stove is 3/4". Therefore any underground larger than that is a waste. My dealer had always used 5/8" underground so that is what I bought from him. 5/8" pex with foam slide on insulation from Lowes. All inside 4" electrical conduit. 
I've never measured my heat loss but the fitting at the heat exchanger can't be grapped when what is flowing.
I heat a 2500+ house with two hot water heaters year round. Use maybe 10-12 cords a year.


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## hondaracer2oo4 (Aug 30, 2011)

You mean the hot water coil is 3/4" correct? The boiler water that goes to the heat exchanger for the house is not in a coil. It is just the water that surrounds the fire box.


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## 1harlowr (Aug 31, 2011)

hondaracer2oo4 said:


> You mean the hot water coil is 3/4" correct? The boiler water that goes to the heat exchanger for the house is not in a coil. It is just the water that surrounds the fire box.


 
Yes the domestic hot water coil is 3/4". But the fittings for the heating water are 3/4" so that really limits the effectiveness of using anything larger than 3/4" pipe.


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## hondaracer2oo4 (Aug 31, 2011)

I wouldn't necessarily say that. (someone chime in if I am wrong please) Those bungs that are 3/4 inch act just like a fitting that you put on the line, say 1 1/4" pex and restrict the flow though that small section of pipe. That would also hold true that you might as well have a 3/4" pipe if the restrictions at the fitting were only 3/4 id.


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## NC4AB (Aug 31, 2011)

The choice of pipe size should be based on the length of pipe, elevation difference, heat exchanger size and pump size.

Going too big does not hurt other than on initial purchase cost, if you go to small you may severely limit the amount of heat that can be moved from your stove to the house. I have a H2 and went with 1" Pex for the piping. 3/4" would have borderline with the TACO pump and my system layout.

Lots of info on Pex pressure drop available on the web, and the installation manuals are available from the Hardy website.


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## hondaracer2oo4 (Sep 2, 2011)

Thank you for your input. The run will be approx. 100 feet total from the Boiler to the Heat Exchanger with no gain or drop in elevation. The Forced hot air oil system in the house is a 200,000 btu unit with a 1.75 gallon per minute nozzle. Now since this is the first year I don't know if this system is way oversized for the house or not but I would assume that they did not install such a massive system for no reason. It is a 1795 colonial with questionable wall insulation. The forced hot air plenum is 25x25, so I will be installing a 24x24 heat exchanger in the plenum. The H4 boiler is rated at 180k btu. So I want to be able to get the maximum amount of heat transfer as possible without limiting myself. Thanks!


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## hondaracer2oo4 (Sep 3, 2011)

So after reading the Taco selecting circulators PDF I have realized that the max flow for 1 1/4 pex is 11.2 gpm. After doing some calculations, in order to get 180k btus with a 20 degree heat loss, I would have to flow 18 gpm. So it appears that getting 180k btus out of 1 1//4 line is impossible. I would have to go to 2 inch line to make that happan and I can't find 2 inch pex anywhere, plus I assume it would be BIG money. So my question boils down to this, If I install a 24x24 HX which is rated for 180k btu and I only flow the max gpm of 1 1/4" line(11 gpm) through the HX, am I going to drop more than the target of 20 degrees on my water temp return because the HX is so huge? Sorry for the newbie questions. Just trying to do this right the first time.


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## NC4AB (Sep 5, 2011)

The oil furnace was propably sized with some safety factor. (Hopefully it does not run 24x7)

Your system will be limited by the weakest (smallest) link. Bear with me on the numbers and feel free to PM me if you need clarification:

If you have the standard Taco 009 pump on the H4 the maximum flow the pump can do is 10 gpm (with 0 back pressure). 

Not seeing how many elbows and fittings are on your system I will take a guess that it is ~300 equivalent feet of pipe worst case (100 ft supply + 100 ft return + 100 ft for fittings). From previous experience 6 gpm in a 1" PEX gives ~ 5.5 feet of pressure drop per 100 ft of pipe so the pressure drop would be 16.5 feet. The 009 is good for ~20 feet of head at 6 gpm so you would be OK.

You are correct that at reduced flow your return temperature will be lower so you will be transfering more heat. Say you have your stove water temperature set at 180F and drop the return to 120F = 60 F drop which is still going to provide you with ~100F degree air which works out magically to ~ 180,000 btu/hr.

On the air side of the heat exchanger you are going to have to be honking some air through the exchanger to get 180,000 btu /hr. Assuming the house is set at 65 F with 100 F exit air temp you will need to move ~4,800 cfm through the air side of the heat exchanger.

I hope that your load is not a continuos 180,000 btu/hr because if it is you will be feeding the stove 24 x 7.

Good luck !!


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## hondaracer2oo4 (Sep 5, 2011)

NC4AB, Thank you for the reply. I just want to make sure that I don't screw myself and put 1 inch line down when I really should put 1 1/4".


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## NC4AB (Sep 5, 2011)

Another place that can hurt the overall system performance is in the selection of underground piping. Invest in the best insulated piping system you can afford, no sense in wasting a lot wood heating the ground. 

There are several good insulated pipe systems available, IIRC they were around $10.00 - $13.00 / foot several years ago. Stay away from the bubble wrap type insulation.


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## hondaracer2oo4 (Sep 6, 2011)

My plan was to do this ********** | Wood Stoves, Fireplace, Pellet Stoves, Gas Stoves and More - Forums! 

Seems like people have had very good luck and the cost is about 3/4 of the good insulated pex lines.


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## hondaracer2oo4 (Sep 8, 2011)

So after doing the calculations it looks like if I go with 1 inch pex and shoot for a 20 degree heat loss I will be getting 75,00kbtu from the heat exchanger. Does everyone feel like this will be enough to provide a 2500 square foot house with questionable insulation? Thanks.


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## 1harlowr (Sep 9, 2011)

I heat a 3000 sq ft house with an H4. I have 5/8" lines 110' from house. The heat exchanger is 100,000 btu. I don't know what my heat loss is back to the OWB but doubt it's much more than 20°. 

Your entire system is limited to the weakest link of the system. ie: how insulated your house is and the smallest fittings in the plumbing.


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