i have a duel side wood/heating fuel furnace with all plastic hose throughout the house for heat and hot water.My problem is no matter how hot the water is it doesn't heat all 3 house zones.If i turn the fuel side on it heats the zones but it blows the pressure valve on the back of the furnace.we have tried bleeding furnace and lines nothing seems to help so far.No heating techs have had the same opinion on our problem so far.What can we do???

we see a lot of questions about this all-in-one deal that is supposed to provide general hot water as well as heating hot water.

there are two different types of usage here, and summary that I have seen indicates that the system won't do it all correctly.

the techs need to go back to manufacturer technical support and make sure the right parts are on this unit. I have a sneaking suspicion that you have got an oversized burner adjustment and/or a wrong pressure relief valve. but it could involve other parts, as I will explain later.

changing the burner nozzle to reduce the gallons/hour rating will reduce the heat rating and should deal with the overpressure.

assuming that the furnace was sized right, and you are pulling the right amount of demand from the unit. which gets to sizing and how the zone controls are enabling the furnace.

this is straining my knowledge, but if you pull heat from 3 zones, you are returning way colder water to the boiler than if one zone only was calling for heat. the boiler has to burn longer, and the water going up to the pumps and to the zones is going to get cooler and cooler. until one zone cuts out, then the next. if the burner continues to cook for one zone as it does for three zones, you are definitely getting hotter water, and perhaps raising heat/pressure until the safeties pop.

what do you have for an accumulator tank, and is it sized right are two other important questions.

I have a very light knowledge based on commercial (hospital) heating with 400 HP boilers across the street. there are banks of accumulator tanks for every zone, and everything is designed for pressures over 500 psi. still the safeties, which go through the roof of the boiler plant, will pop off occasionally. roars like a train in a tunnel.

this is why I say tech support from the vendor needs to be brought in, and perhaps supplied with some logged temp information. stumbling bozos playing with that thing are not what you want.

This message has been edited. Last edited by: swschrad,

THANK YOU for the info. The vendor of my oil/wood furnace no longer responds to my emails asking for help or information, i would even be willing to hire someone he recommends to work on the system even though he is not local. I am not sure what the accumulator tank is, is it the expansion tank? I have had the system for about 5 years now and it worked well for about the first 2 years. I have not found a heating tech that i feel is knowledgeable about the system and none have mentioned contacting the manufacturer which makes a lot of sense. The last tech, which was last week changed the expansion tank after i complained about the 007 circulator pump on the basement zone making a strange noise and being very hot, i had no heat in the basement and still have no heat in the basement. This tech wants to bring in a second tech to help him change the pump, i will not be asking this tech to work on my system again!

yeah, accumulator = expansion tank.

which safety is popping off for you, for the potable hot water or the heating loops? if it's the potable (tub/shower) hot water, if there's not an expansion tank there, you should have one on this type of system.

it would be my sure preference, based on my old maintenance helper days, to have the popoffs drain straight above a floor drain, and have one of those "doggie cone" drain covers on it to reduce splashing.

This message has been edited. Last edited by: swschrad,

I believe its the tub/shower water thats popping because its the pipe that comes out the top of the furnace and then goes down the back of the furnace and ends about 6 inches above the floor.The exp tank that we have is about 3 gallons in size.The bladder in it is about half way down inside it.That also sits above the furnace and off to the side about a foot away.One of the techs that we had working on this said it would be a better idea to have a whole bank of dump zone piping.Dont know if thats such a a good idea??

I'd go up to a 12 gallon tank and see if that solves the issue. ideally you would have a professional plumber evaluate the situation and make a recommendation. a 3 gallon expansion tank is probably only good for a light expansion of a gallon or so before you start getting into a popoff situation.

and check the valve against code in that area. that safety system needs to be looked at as a system, not fiddle with pieces until the floor stays dry. that could end up with a blowout. last one I saw pictures of in the newspaper was an 80 gallon electric heater that blew a 2 story house apart.

it all boils down to balancing the system.
on the return side of each zone is a balancing valve
its a ball val;ve with numbers on it. also refered to as a circuit setter
if your valves are wide open. the water is flowing to fast thru the zone to heat the area properly. you have hot water but its going to fast.
locate your zone valves. they should be all togather beside the boiler. and if installed correctly be marked as to what valve serves what zone.
you can try and throttle them down by your self. but you really need a tech. [like me]
to put gages on it and set the gpms correctly
call your local hvac guy, tell him you have a hydronic system that may need to be balanced
you only need to have around 30 psi on your system, depending on length of piping and sq ft of house
any more than that you will pop off your t&p valves. sounds like your doing that already
turn the pressure down,slow the water down. its ambient heat...not forced air

This message has been edited. Last edited by: Frodo,