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[Dnors180]

disclaimer...i am completely new to the entire outdoor wood furnace/boiler scene. We just bought a house (over 5k square feet of heated space), the house has a boderus furnace (oil)  in the house and outside has an Aqua-therm sheltered wood furnace (not sure of the model). 

Here is what is happening. the furnace temp is set at 190 (back of the furnace)  the aqua stat that is inside the house (the overtemp one that redirects to the attic in case of overtemp) is set at 195.  Any other settings and the furnace will vent out of the over pressure vent.  The previous owner had it set at 195 outside and 200 (max) on the inside. when the system is running the pressure in the system is 20 psi inside the house and 22-24 psi outside at the furnace.

I have replaced the pressure relief valve (i should say, my plumber has replaced it) and he has looked over the system and can come up with not other reason why it would be venting off at those temperatures if the previous owner was able to run it at those temps.

Am i missing something easy here? I'm sure i have not given all the info needed and i appologize in advance for not knowing all the nomenclature.

[slimjim]

There are several reasons why you may be overpressurizing, my first guess would be overheating due to fresh air coming into the firebox when the boiler is in the dormant mode, how are your door gaskets. second guess, faulty aquastats, have you checked the actual water temp against what the aquastat says it is, you may be low on water and the aquastat is not registering the water temp because it is not submerged in water but air instead, check these things and let us know what the outcome is.

[Dnors180]

slimjim,

thanks for your reply,  I replaced the door gasket and the gasket between the blower,  I have not replaced the gasket on the ash door but i could not see or feel an air leak (i will replace it tonight). 

the aqua-stats are all analog and do not give me a reading.  the only place i see an actual temperature and pressure reading are on the front of the stove and in the house near the oil furnace.  Is there another way to check the temp without replacing parts?

[MattyNH]

Aqua-Therm owner here..Plain and simple your running your boiler too hot....You dont have the demand Thats why your dumping water. Only time pressure relief valve should be replaced is when it has a constant drip......Its a temp thing..Your pressure range is with in range..No different than oil boiler range! You can lower the pressure by dumping water manually to lower pressure..Put your boiler at 180-185...Youll never have a problem with the relief valve popping(which its designed to do) unless you lose power etc etc ..

[slimjim]

not a really accurate way, are you full of water?

[MattyNH]

not a really accurate way, are you full of water?

What you mean not accurate way?

[slimjim]

No really accurate way to measure the water temp inside the unit at the point of the aquastat other than pulling the old one and putting in a new one that I am aware of, perhaps you can help as you have one.

[MattyNH]

No really accurate way to measure the water temp inside the unit at the point of the aquastat other than pulling the old one and putting in a new one that I am aware of, perhaps you can help as you have one.

Well the the pressure relief and temp relief valve is designed to pop and a certain temp..Just like the ones on the oil boiler...and the OW boiler does have a water temp gauge/pressure gauge..Just like tonight, Mentioned in another post..I burned cardboard...Yeah my temp relief valve popped..Its designed to do that...

[slimjim]

I think what he is asking is why does the relief valve pop under normal operating conditions, we are trying to make it better not test the relief valve by overheating the unit, please check to be sure you are full of water, is there a low water indicator on the unit.

[MattyNH]

I think what he is asking is why does the relief valve pop under normal operating conditions, we are trying to make it better not test the relief valve by overheating the unit, please check to be sure you are full of water, is there a low water indicator on the unit.

Running 20 psi or so as he mentioned..he has plenty of water..Hes running his boiler too hot..

[RSI]

What kind of expansion tank do you have? If it has a bladder, I would check to make sure it didn't fail. If doesn't, I would make sure it as enough air in it.

If that is all good, I would lower the set point down to 180 and see if it is overshooting much.

[Dnors180]

Gentelmen,

Thanks for the replies, I have had the expansion tanks checked by a plumber and he says that they are good.  I will have to agree that i think i'm just running it too hot. I found out that my mother in law has been loading it during the day.

My other question is...If there is not a demand for heat, the unit should just sit and smolder right?  and if it is reaching a certain temp and causing the PSI to push past 30 causing it to blow off, should i lower my PSI to say 16 or 18? (if thats even possible)

[slimjim]

After re-reading the original post, he has already dropped the temp 5 degrees from where the original owner had it set, there is probably a reason that they had it set @ 195, I'm thinking that the home heats hard with not enough radiation in cold weather @ the lower setpoint, good point with the expansion tank, it may be bad or just not big enough. As far as looking at the pressure to determine if the unit has enough water in it, 1 gallon of water creates 800 gallons of steam, I may not be an expert on that unit but I bet it does not hold 800 gallons of steam without building pressure, I would check that it has enough water in it as the aquastat bulb may not be in the water and then check that the aquastat is accurate.

[franky1]

 I will have to agree that i think i'm just running it too hot. I found out that my mother in law has been loading it during the day.
 
wow,,must have a good inlaw,,if she does that!!!

[Dnors180]

franky1.....dont get me started on her good deeds