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jeffro83 08-27-2012 03:15 PM

Boiler system not completely filling?
Hey all. I'll try and provide as much information as I can about my situation, and I hope you can bear with me!!

Less than 3yrs ago, I had a Buderus GB142 installed in my old character home's basement, to replace the 40+yr old boiler that was in there. Has ran fairly well, with a few hiccups here and there, mostly to do with the old rad system in the house. Replaced some visible sections of piping in the basement, had a couple isolating valves put in around some rads, replaced the fill valve in the basement because it didn't seem to keep pressure right at the setting I'd had it at, 14 or 15psi, I believe. Nothing too too major. Moved away from home, and have continued to rent out the entire house.

Just before I moved, about a year ago, I had a Triangle Tube Smart50 indirect water heater installed alongside my GB142. Before I left town, I made sure everything was in proper operating order. All has been working well with both until about a month ago, when my tenants noticed there was no domestic hot water (the space heating feature hasn't been used since the winter, but the boiler still operates in the warm months, to provide domestic hot water).

I flew home for a visit, and ended up doing a whole whack of other unrelated reno's, along with trying to figure out the boiler/water heating issue. The rad system had zero water pressure. Used the filling valve (pretty sure it's a Watts 1156F) to refill the system. Could hear it gurgling for a good while, as I filled it.

Could hear water getting to the top loft rads (2 of them), and they just stopped filling. No more air came out of the auto bleeders I have up there; no water - it just stopped filling. Any more water I tried to fill would just quickly build pressure, as if something was blocked.

I thought maybe there was an airlock in the system somewhere, so I drained the entire system, and started from scratch. Same issue happened though.

Was then wondering if it was just the auto bleeders stopping the flow of water at the top of the system (which they're supposed to do) but I remembered after installing the autobleeders, I refilled the rads, and had seen bits of water spitting out of them when the pressure had maxed out. Not to mention, I've never seen the pressure build so quickly on the basement gauges after the rads stopped bleeding on the top floor.

Anyway, I had the rad system mostly full of water, so the domestic hot water system would work (there was now ample water pressure for the boiler to run on that water circuit). I had to fly back across the country where I now live, and thought I might be OK with the rad system. Pressure was staying, hot water working.

A couple weeks later, got an email from a tenant again. No hot water. The water pressure was down to nothing again. Walked him through the process of refilling the water system so they could get hot water again. Something is obviously up, and I'm not back in town to troubleshoot. Crud blockage somewhere in the pipes? Serious leak somewhere in the rad system with no apparent location of where it's going? What's happening to my water pressure in the rad system??

1: I now live 2500km away from my rental house and can't easily run over to the house and troubleshoot!

2: haven't been able to successfully get in touch with the original plumber who installed the boiler, and set it far as I know, he's the only one in town who was able/licensed to work on Buderus boilers?

3: all the plumbing companies in town seem quite nervous to work on a system involving a Buderus boiler; I have yet to actually talk to a company in town who has even HEARD of the Buderus name, so they all refuse to work on my system while the boiler is still under warranty.

Any suggestions for a landlord running out of options?...

Acomfort 08-27-2012 03:18 PM

the only time I've come accross a similar issue was a small air pocket in the sytem, once we were able to remove it, the system worked.

jeffro83 08-27-2012 03:36 PM


Originally Posted by Acomfort (Post 997607)
the only time I've come accross a similar issue was a small air pocket in the sytem, once we were able to remove it, the system worked.

Thanks for the reply. Not sure how else I can empty and refill the system to get rid of any other potential pockets of air...any suggestions on a foolproof way to do it?

And I guess that doesn't really explain why the water pressure keeps dropping from ~15-17 psi down to zero.

hvactech126 08-27-2012 05:24 PM

its dropping pressure do to a leak. First thing to do is find the leak.

beenthere 08-27-2012 06:40 PM

Either a leak. Or if you have a bladder expansion tank, the bladder may be bad.

DannyT 08-28-2012 08:23 AM

when you say loft you mean on the second floor? you lose 5 lbs of pressure for each floor you go up. if the boiler has 14 pounds of pressure in the basement at the floor of the second floor you will have 4 pounds. i used to have to raise the pressure up to 25 to 30 lbs in order to bleed 3rd floor radiators then drop it back to 12-15 for operation.

techpappy 08-28-2012 06:57 PM

You are losing water from a normally closed system with no sign of where that much water is going to, which leads me to believe one of two avenues..
1. Safety valve leaking to a drain..if so, replace it..can't be repaired .2.leaking through domestic water heat exchanger...not good! Also, slow leaking drain valve at system or boiler..not too bad

Will try to elaborate on troubleshooting...1. turn off boiler. 2.Fill boiler system until it is full and re pressurized . 3. Drain domestic hot water portion of the DHW heater and open the drain or inspection port? to see if water is leaking through the heat exchanger..if it is then that is the source of leak and appropriate repair/replacement of heat exchanger required...You may have to restart the boiler with the DHW heater still drained and open because may require some heat to cause possible crack to open up b ut, nor likely...As for filling the heating system ..remove one of the radiator air vents at top of system and open system fill line..if it doesn't flow out top then , either not enough supply pressure or plugged heating line,,,I suspect Pressure Regulating Valve..could install bypass to fill faster then revert to PRV once pressurized. Also you could put some food dye in heating system and see if it comes out at domestic hot water tap. That would prove leak at heat exchanger..I will reply again if I can think of anything else

techpappy 08-28-2012 08:09 PM

EUREKA!! You likely have a flooded cushion previously mentioned, .if non bladder type..this can be caused by pinhole or most likely corroded or fitting leaking the air out at the tank...OR if bladder type, the bladder is ripped/leaking. Either way this prevents an air cushion and just floods the tank..this would explain the quick rise in pressure and also results in no cushion/room for expansion of water when it is heated. You can't compress water so, pressure just rises that's why cushion tank required Therefore it will result in over pressurization when the water heats up which will then cause the safety valve to open to relieve the pressure results in the loss of water. Get plumber to check cushion tank ..if bladder type just drain and apply air pressure to see if it will hold..if true air cushion type then check and tighten all fittings, particularly at top of tank OR guage glass if equipped..drain and refill..should provide cushion of air when system refilled ..if pressure shoots up rapidly then still no cushion tank..

jeffro83 08-30-2012 01:51 AM

thanks for the replies, folks. really appreciate the advice. i'll try and get a plumber in to check the expansion tank (yes it's a newer bladder type, installed when the new boiler was put in).

i find it really difficult to imagine there's any kind of massive leak in the heating system right now that would be making me lose so much pressure/volume of water. obviously i can't be sure, because i'm not there to see what's going on, but we'd be talking about a LOT of water that's mysteriously missing over just a couple weeks - when i tried refilling the heating system when i was last in the house, i basically filled 3 or so entire radiators. it would be gallons and gallons, that hasn't turned up anywhere?...

dannyT, yes when pressurizing the system, i'd have to almost max out (before the relief valve would release water @ 30psi) to get water flowing to the top floor. usually around 28psi would normally fill it, and i'd have it set at around 16psi or so thereafter. when i say loft, i mean top floor...the house is actually 3 floors. basement, main floor, second floor, 3rd floor loft. so yes, lots of pressure needed to get water to the top.

also, i vaguely remember one of my tenants saying there was a small bit of water (maybe an ounce?) coming from the threaded air vent of the indirect heater. that didn't sound right either. is there supposed to be an expansion tank between the boiler and the indirect as well? the plumber who installed the indirect said there wasn't a need for it?

techpappy 08-31-2012 11:56 AM

This is what is happening to account for water loss.

Boiler/system water is at approx room temperature on initial start up. As it warms up the pressure rises rapidly because there is no air cushion in the system..the water needs to have room to will not compress therefore the pressure rises above the safety valve set point of 30 psi and exits to the floor or possibly to a drain where it is not noticed. The safety valve will reset once the pressure drops however, the process repeats every time the boiler starts up again It's that simple. Believe me.I am currently retired but, have carried out boiler and related equipment inspections for over 40 years. The only other situation for large water loss that I found was when a fill vent valve was left open at the top of a system. It was also piped to a drain and not found for over a year when I was called in to troubleshoot. It could also be possible that any other shut off valves or circ pump could have a slow leak somewhere but, I don't think so especially when you indicated the rapid rise in pressure. Classic sympton of bad cushion tank.

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