Oil Hot water furnace PSI over 30

Kailerfey

First of all, please excuse my ignorance as this is not my area of expertise! 

I have a Dettson hot water furnace that's system psi has been steadily creeping up and over 30 psi (should be 12) and setting off the pressure release valve. I have managed to relieve the pressure by draining the expansion tank but it just keeps going back up to 30+ within a few hours. Even when the furnace is manually shut off. The only way to stop the pressure from increasing is to literally shut off my water. 

I can provide any additional details but I figured I'd start somewhere! 

Thanks so much in advance!

DJD775

Sounds like you either have a leaking domestic water coil or a bad pressure reducing valve. If the problem is happening when the boiler is off you can rule out a bad expansion tank. Either way, call a pro and have them come out and properly diagnose it.

Kailerfey

DJD775 said:

Sounds like you either have a leaking domestic water coil or a bad pressure reducing valve. If the problem is happening when the boiler is off you can rule out a bad expansion tank. Either way, call a pro and have them come out and properly diagnose it.

Thank you so much for your insight! I'm waiting on a technician, it's hard to get one in my area they are in very short supply.Hopefully they will be able to come out by Friday. In the interim I'm just trying to figure out the best way to still have hot water but not screw anything up or make it worse. 
I tried turning off the lever that let's hot water come directly to my tap upstairs and it seemed to stop the pressure from increasing. Could this mean the pressure relief/reducing valve is not the issue and instead narrow it down to being the leaking domestic water coil? 

pecmsg

Is this an Expansion tank or bladder tank?

Expansion tanks mount on the ceiling between the floor Joice.
Bladder tanks on the piping.

HomerJSmith

When you fix it be sure and replace the Pressure Relief Valve.

Kailerfey

pecmsg said:

Is this an Expansion tank or bladder tank? Expansion tanks mount on the ceiling between the floor Joice. Bladder tanks on the piping.

It is an expansion tank.

Kailerfey

HomerJSmith said:

When you fix it be sure and replace the Pressure Relief Valve.

Do you mean this? 

Kailerfey

pecmsg

Did you Completely drain the tank or just lowered the pressure?

WMno57

pecmsg said:

Did you Completely drain the tank or just lowered the pressure?

Right. There should be a valve to isolate the tank from the rest of the system. Close the isolation valve, then open the drain valve. Leave the drain valve open for a while. It will gulp, glurg, and burp for awhile while all the water drains out.
Then close the drain valve, and open the isolation valve connecting the tank to the rest of the system.

Kailerfey

WMno57 said:

Did you Completely drain the tank or just lowered the pressure?

Right. There should be a valve to isolate the tank from the rest of the system. Close the isolation valve, then open the drain valve. Leave the drain valve open for a while. It will gulp, glurg, and burp for awhile while all the water drains out. Then close the drain valve, and open the isolation valve connecting the tank to the rest of the system.

We did drain it completely and it did make all those sounds and left it for about 4-5 hours before opening it back up again. A few hours after the pressure went back up over 30. 

WMno57

OK, good. I think you have ruled out the tank as the problem. At this point, possible suspects are a failed Pressure Reducing Valve (PRV) that supplies water to the boiler, or a leaking coil for the domestic hot water. (as mentioned a couple posts up by @DJD775 )
To rule out the PRV;
There may be a shutoff valve upstream from the PRV. If you close this valve and pressure still rises, that points to a leaking domestic hot water coil.
If leaking coil, then one possible solution for you is to get a dedicated water heater that is not part of your Dettson.

Kailerfey

WMno57 said:

OK, good. I think you have ruled out the tank as the problem. At this point, possible suspects are a failed Pressure Reducing Valve (PRV) that supplies water to the boiler, or a leaking coil for the domestic hot water. (as mentioned a couple posts up by @DJD775 ) To rule out the PRV; There may be a shutoff valve upstream from the PRV. If you close this valve and pressure still rises, that points to a leaking domestic hot water coil. If leaking coil, then one possible solution for you is to get a dedicated water heater that is not part of your Dettson.

Thanks so much for all your help! I think that's what I tried last night.. not sure if the pictures will help but when you say upstream, you mean the one that directs hot water to my tap (bypasses the system)?

WMno57

Your Dettson boiler heats both the water that heats the house (space heating) and the domestic hot water that goes to the taps.
These are kept separate by the coil. The pressure gauge on the boiler will show the pressure on the space heating side. The pressure on the domestic water side is higher. If the coil has a leak, water from the domestic water system will leak into the space heating side and raise the pressure on the gauge.
If your system has a valve to shut off water to the space heating side of the boiler, domestic water will still be supplied to the coil. If the coil is leaking, the pressure on the gauge will still rise.

WMno57

The coil is the square to the left of the gauge. The two pipes coming out the top of the Dettson are the inlet and outlet for space heating.

Kailerfey

WMno57 said:

The coil is the square to the left of the gauge. The two pipes coming out the top of the Dettson are the inlet and outlet for space heating.

I understand! So it's that yellow valve that is for the domestic. Is it safe for me to shut it off overnight for example while I wait for it to be fixed? Thanks again for all the help! 

WMno57

Kailerfey said:

So it's that yellow valve that is for the domestic. Is it safe for me to shut it off overnight for example while I wait for it to be fixed?

When the yellow valve is closed there will be no water at the hot taps. Pressure on the domestic water side of the coil will drop to zero if a hot tap is opened when the yellow valve is off. Now the direction of leak is reversed. 30 psi on the boiler side will inject stagnant boiler water into your depressurized domestic water system.
So when the yellow valve is off, don't open the hot taps. Better yet, don't drink the water until your system is fixed and you have run some water through the domestic taps (faucets).

Big Ed_4

Shut off the boiler feed until the tech arrives . It should temporary stop the releasing of water . The two bell photo is a duel valve , shut off the valve upstream from that valve.