Baxi HT 380 losing internal water pressure while sitting idle, then E119 code

ceepaul

As my Baxi HT 380 sits idle from no demand to heat the house, the internal pressure falls into the zero bar zone. This may take a couple hours with no activity on the unit for either heat or hot water. Unit temperature inches down to 20 or 30 c. Once the pressure gets in the middle of the zero bar zone, it locks out with E119 and we cannot get hot water. I must then turn up the house thermostat to cause the unit to fire up. The temperature immediately starts to rise and the bar will jump to the 1 or 2 bar zone and we can then get hot water from the tap. This has been a chronic problem and over the past several months the repairman has replaced the pressure valve, sensor, mother board and installed an external expansion tank. What is the problem and how do we fix it? The local plumbing supply Baxi expert is running out of ideas also. The unit was installed about five years ago and had been running fine. Any help will be greatfully appreciated.

hot_rod

pressure in the boiler drops to 0? must have a slow leak somewhere. When the heating circ starts it adds some pressure differential, enough to allow the DHW HX to work?

I have a Laars Mascot, I think it is a Baxi rebadge, I'll look and see how it is piped inside for DHW. I think it has a 3 way zone valve that toggles to a plate HX on DHW call. A flow switch on the water caused the 3 way valve to toggle. When you open a hw faucet, can you hear or see the zone valve operate?

Tom_133

Did your repairman replace the internal pressure tank? Adding and external is a good idea for the heating side but does nothing for the domestic side. My guess is the internal expansion tank is bad, and the relief valve is either dripping slow or internally something is dripping. The fact that you didn't have an external expansion tank from the start indicates that the internal has always done more than it should and is most likely bad. The downside of all the baxi's is the lack of auto fill during domestic water heating and in the summer with no heat being called for this can be a real problem.

ceepaul

hotrod
the pressure drops down to the center of zero bar and then system locks out with E118. Yes, when I turn up the thermostat the boiller fires and water pressure on bar jumps to 1 or 2, so then we can draw hot water. I don't see a 3 way valve to toggle. It has two black level ball valves underneath to shut off water supply to/from unit.

Tom
Last June we could hear the internal expansion tank rushing air/water so figuring it was bad, he added an external tank. It worked OK through the summer but started showing pressure loss in september. Being advised that we had an internal leak, we replaced the flat plate exchanger however problem continues. We don't show much at all of water overflow from release valve nor can I see any water moving up through the condenser tube.

Tom_133

So you never replaced the internal tank? The internal tank is there for hot water production. An external one won't do much to help the boiler during hot water production. Thats why when you turn on the heat it kicks on, the 3 way valve moves over to the heating side and the auto fill will fill the boiler and allow it to fire up. I would change that internal tank, and sadly they aren't cheap.

GW

If you're losing water you have a leak, gotta find it. Don't spend anymore money till you have the leak issue dealt with.

Isolate your heating system and see if the needle drops.

ceepaul

Tom, GW
It is starting to make sense. We never removed or replaced the internal expansion tank after we added the external tank. Today I turned the stat down so it would not demand heat then switched the electronic zone command to "manual". After two hours of non-use the water pressure did not move down at all and stayed in the 2 zone. I am getting a little more spill over from the high pressure relief, something that I haven't normally seen in the past. I have not found any leaks throughout the baseboard system or outside of the unit. Our information here is pointing towards the old internal expansion tank. We won't be able to do much more until next week, but I will keep you posted. Winter is still holding back a bit here in Vermont.
Please let me know if my test with the zone switch above means anything.
thank you
paul

Tom_133

Paul

I am located in Central Vt, let me know if I can help.

Tom

GW

Ahhhhhh I didn't catch that if you mentioned that in an earlier post. If you're dumping out of the puker when the boiler fires it's time for a new exp tank. Be sure to double check the air pressure before installing the new one, per baxi technical rep.

BTW you may get lucky and buy some time, drain the pressure off the boiler and get your bicycle pump, crank it back to 15 psi. May or may not work. You may need a truck tire fitting to get in there

Good little boiler, we service several

ceepaul

Tom, GW
We just were able to replace the internal expansion tank. Water pressure is holding and hot water flow is more responsive and consistent. This has been a learning lesson even for the repairman who was working with a Baxi tech . My come away here is if the internal tank fails, it needs to be replaced. Adding an external tank is OK, but internal expansion tank must be working properly to service the faucet hot water.
Thank you all for all of your assistance. This has been a haunting problem and you helped us get through it.

paul

GW

Paul, very good, we all go through the learning curve; the toils of living in a 1st world nation.

Thanks, Gary

Tom_133

Great to hear!! Thanks for posting the fix, it may help others in the future.

ceepaul

Still working fine. Hot water comes faster and is steady. Doesn't fluctuate as it did before replacing the internal tank.
paul