Installing pressure Tank on Harmon Indoor wood Boiler

[pinesawyer]

A few years ago I installed a Harmon wood boiler in my barn and tied it into my oil boiler in my basement. Piped it under the drive about a hundred feet. The Harmon is rated for heating up to 3,000 sq.ft. However, my cabin is only about 1500.

The unit is great and saves me a bundle, but the pressure always ran high. At 190 degrees (where the aquastat is set on wood boiler) my psi is about 30 to 32 inches. Well the pressure release trips at 35. So I am always worried. Some people have told me that kind of pressure is good. Others said no way. Way too high.

Last spring, after throwing my last load of wood in the boiler for the season, I walked away, jumped in my truck and went to work...forgetting to shut the ash pan door. Well the pressure release valve did not release, and I blew both my inlet and outlet and spewed all my antifreeze onto the cold concrete floor. Wife, lookng out the window, thought the barn was on fire. Steam coming out of everywhere.

So this week I have to get the boiler back online. I am making a few modifications. I have two major questions.

One. If I install an inline pressure tank at the wood boiler in addition to the one already inline on the oil boiler, will this reduce my overall pressure.

Two. The pressure release valve failed last spring when I forgot to close the ashpan door. If it had worked as it should have the valve would have just kept popping and knocking the pressure down until the wood in the firebox burned out. Yah, definately not fun, loss of antifreeze and all, but I would not have blown my lines off the boiler. So is it possible to put a back-up pressure release valve in the system or do they make really, really, really good pressure release valves that absolutely do not fail.

I thought they were pretty much all the same.

Any and all thoughts suggestions are appreciated.

Thanks

 

[leon]

Harmon boiler

Which Harmon do you have? The 360? you can buy a
firebox reducer if desired.


Installing a second pressure tank will make no difference
in boiler boiler operation and will be counter productive
cost wise.


You would be better off installing a Harmon atmosperic
water storage tank that is not using pressure to regulate
the water flow.

An atmosperic system with a manual adjusted or
automatic water level using a float is less trouble
and it just requires a bit more oversight where the
pump(s) simply circulate the heated water and do
not have to fight with a higher head pressure due
to pressure regulator and the exothermic reaction
of heating water.


You should not require antifreeze as the system cannot freeze
and rupture due to the atmosperic tank.

Having learned what I have about my wood and coal boiler,
I would have never switched to a pressurised storage system from an
atmosperic one as the atmosperic is less trouble and much less likely to leak
as you are only dealing with heated water and no pressure.


There are many grades/manufacturers of pressure relief valves and if you do not manually exercise the valve occasionally under heat and pressure they will fail/not open.

You should investigate McmasterCarrs catalog for relief valves if you intend to continue with a pressurised system.

 

[hanniedog]

I run a Harmon 360 with around 7-10lbs of pressure. Does your system have a auto fill water valve if so it should keep system at or under 12lbs. 30 lbs is way to much.

 

[pinesawyer]

Which Harmon do you have? The 360? you can buy a
firebox reducer if desired.


Installing a second pressure tank will make no difference
in boiler boiler operation and will be counter productive
cost wise.


You would be better off installing a Harmon atmosperic
water storage tank that is not using pressure to regulate
the water flow.

An atmosperic system with a manual adjusted or
automatic water level using a float is less trouble
and it just requires a bit more oversight where the
pump(s) simply circulate the heated water and do
not have to fight with a higher head pressure due
to pressure regulator and the exothermic reaction
of heating water.


You should not require antifreeze as the system cannot freeze
and rupture due to the atmosperic tank.

Having learned what I have about my wood and coal boiler,
I would have never switched to a pressurised storage system from an
atmosperic one as the atmosperic is less trouble and much less likely to leak
as you are only dealing with heated water and no pressure.


There are many grades/manufacturers of pressure relief valves and if you do not manually exercise the valve occasionally under heat and pressure they will fail/not open.

You should investigate McmasterCarrs catalog for relief valves if you intend to continue with a pressurised system.

I have no idea what you mean by atmospheric system. Mine is a SF260. And there is a a water make up valve installed on the oil boiler system. When all valves are open and the wood boiler is burning it essentially is one closed pressurized system. If adding another pressure tank into the system wont have any affect, what about just adding more linear feet of baseboard? But if I don't need it and the zone is closed it won't make a difference on the pressure will it?

Where do I install the Harmon atmosperic pressure tank?

Thanks for your help.

 

[hanniedog]

Hes talking about going to a non pressurized system. I would leave your system as it is myself. My setup has a second expansion tank above the wood burner. I would check the autofill valve because there should not be that kind of pressure in the system. Did you do the plumbing yourself or have another person do it.

 

[NCPABill]

Funny, I just plumbed for my expansion tanks, and was surfing for confirmation before I bought them. Here's what I understand, simplified:

Your system has a total volume, which when multiplied by .04 equals the total acceptance volume of the pressure tanks required. Note that this is not the total tank volume, but approximately one half of the listed tank volume, more or less. In my case, with a 500 gallon storage tank included in the system, I need 24 gallons of acceptable volume. In order to do this, I plumbed from the bottom of the air scoop to several tees, each of which will have an expansion tank plumbed to it. My system will have three tanks total. I understand that it is important to have all required tanks in one location, thus the plumbing line in place of the standard "screw-the-tank-into-the-air-scoop" style usually seen.

You can put in multiple T&P valves, again based on my understanding. I place them where is it convenient to plumb them in, and where I don't mind the blow-off potential. I wonder if the system pressure being so close to the relief pressure somehow compromised the valve? I think that you want to release some water to the 12psi cold setting. When it gets heated, it will expand, thus the need for the expansion volume being based on the acceptance factor.

Good luck getting it straightened out. Winters 'a comin'!

Bill

 

[hanniedog]

NCPABill what make boiler are you running?

 

[leon]

boiler in a barn

I have no idea what you mean by atmospheric system. Mine is a SF260. And there is a a water make up valve installed on the oil boiler system. When all valves are open and the wood boiler is burning it essentially is one closed pressurized system. If adding another pressure tank into the system wont have any affect, what about just adding more linear feet of baseboard? But if I don't need it and the zone is closed it won't make a difference on the pressure will it?

Where do I install the Harmon atmosperic pressure tank?

Thanks for your help.

You will not need any extra baseboard.


The open to atmospere vented boiler storage tank is an open
to air system using a non bladder storage tank with an air vent to equalise
system pressure at all times with a manual water make up valve.
The tank is positioned above the boiler and it has a vertical water
level tube to indicate the system water level at all times.

The system only has heat and the actual head pressure created by the
circulating pump to heat the dwelling.

The system is simpler as it does not require constant bleeding of air
repeatedly as the hot water created by the boiler pushes the air out
of the system into the non pressurised tank which vents to the
atmosphere if needed.

The use of pressurised system is problematic in that you can get a slug of
air and it takes forever to bleed it because the gas bubble created prevents
movement of the heated water until it is bled out and gone

The other issue is tiny temporary leaks in pressurised systems from
overheating and how aggravating they can be.

Your Harman dealer has or should have the information the non pressurised
system used by Harman for their line of wood and coal boilers or you can
buy a system from the Harman dealer in Montour Falls, N.Y.

 

[pinesawyer]

You will not need any extra baseboard.


The open to atmospere vented boiler storage tank is an open
to air system using a non bladder storage tank with an air vent to equalise
system pressure at all times with a manual water make up valve.
The tank is positioned above the boiler and it has a vertical water
level tube to indicate the system water level at all times.

The system only has heat and the actual head pressure created by the
circulating pump to heat the dwelling.

The system is simpler as it does not require constant bleeding of air
repeatedly as the hot water created by the boiler pushes the air out
of the system into the non pressurised tank which vents to the
atmosphere if needed.

The use of pressurised system is problematic in that you can get a slug of
air and it takes forever to bleed it because the gas bubble created prevents
movement of the heated water until it is bled out and gone

The other issue is tiny temporary leaks in pressurised systems from
overheating and how aggravating they can be.

Your Harman dealer has or should have the information the non pressurised
system used by Harman for their line of wood and coal boilers or you can
buy a system from the Harman dealer in Montour Falls, N.Y.

Thanks for your advice and comments. I fitted my boiler and just put an expansion tank at the wood boiler in addition to the one on the oil system. I put a valve on it so I can take it off-line if I need.

Thanks again, and I will let you know what happens. I am ready to burn.