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G4 valve blowing off

Air Source Heat Pumps (ASHPs)

Last Post by David999 2 years ago

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David999

(@david999)

Reputable Member Member

Joined: 2 years ago

Posts: 348

Topic starter 21/10/2024 10:21 am [#1784]

My system is making a loud fog horn sound for about 3 seconds, too short for me to get to it to identify what’s going on. I think it’s the g4 valve with the basket on it, I checked outside and no signs of water. Is there any other devices that would make that sound around the expansion vessels etc and is that normal to blow off. Only caught it twice so far once yesterday and again today.

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Richard24738

(@richard24738)

Estimable Member Member

Joined: 3 years ago

Posts: 104

21/10/2024 12:31 pm

Not sure if it's the same as you but I get a one off loud fog horn sound when flushing the toilet or running a tap.

It only occurs after DHW heating, not always though.

The Mitsubishi service engineer suggested a "System Shock Arrestor".

Install 13 April 2024 - 4 Bedroom Brick Detached - Heat Loss 9,281w, Design 45c at -2 - Ecodan 11.2kw R32 - 25L Buffer - 250L Telford Tempest HP DHW - All 16 radiators replaced - Auto Adapt - Mel-Pump app - Octopus Cosy Fixed
10 March 2026 - now 2 x Sigenstor 10 batteries with 8kw Inverter

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David999

(@david999)

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Joined: 2 years ago

Posts: 348

Topic starter 21/10/2024 12:44 pm

Just noticed I have lost my pressure and had to recharge. I have a thought it’s the mains water pressure that’s too high.

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Toodles

(@toodles)

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Joined: 4 years ago

Posts: 2958

21/10/2024 2:09 pm

@david999 Recharge what? Your circulating fluid to your emitters? If yes, then something odd would be happening as the circulation system is normally pressurised to approx. 1.5 bar and then both of the valves (one on either side of your pressure vessel) are shut off so you then have a closed system. Higher main pressure should not then influence this circuit at all. Have I mis-understood your question perhaps? Regards, Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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David999

(@david999)

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Joined: 2 years ago

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Topic starter 21/10/2024 2:50 pm

@toodles a bit confused toodles, no idea what’s blowing off the expansion vessel of the tundish but it was loud. I checked my pressure on the gauge at the filling loop and it was zero so I filled it back up but over did it and let a bit off. It came out the pipe outside and no antifreeze in it, but could be just because I just filled it up and the loss could just be me draining air off the other day when I first heard it blow off. Am I correct that the tundish is just for the cylinder and no antifreeze in that side and it could be my supply pressure creeping up.

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Toodles

(@toodles)

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Joined: 4 years ago

Posts: 2958

21/10/2024 3:02 pm

@david999 I think the more knowledgable need to answer this one as I am not sure I understand what is happening. Don’t want to cause you more problems, I expect some other readers will know what is going on. Regards, Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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David999

(@david999)

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Joined: 2 years ago

Posts: 348

Topic starter 21/10/2024 3:20 pm

@toodles the installer coming out tomorrow toodles. I was curious if the tundish routinely blew off or if it’s a fault but looks like a fault or they wouldn’t come out I guess. Due a service soon so hopefully the samsung authorised blokes sign it all off as satisfactory. My installation guarantee expires in November so need to ensure all is well. I’m learning the system but a bit to go yet.

if someone else replies could they clarify two other points please.

1. is the expansion vessel with the filling loop only for the radiator side.

2. Is the tundish only for the domestic supply in the cylinder, the stored water. It must be the mains pressure that pushes it out and the tundish protects the cylinder?

3. Blowing off at the tundish will not lower the system pressure in the rads? I think it was me bleeding air and getting the two mixed up.

if anybody has a thermal solar, what’s their outputs, I’m getting about 40c at the minute for a 20 tube system

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David999

(@david999)

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Joined: 2 years ago

Posts: 348

Topic starter 22/10/2024 10:29 am

Heating engineers out today and my fault is the expansion vessel for the dhw cylinder. It started making this noise like a foghorn on Saturday and has gotten worse, but tied it down to when hot water is run, but it only sounds for a few seconds. A thing to check if you have a bicycle pump with a gauge is the pressure in the vessel, it has a standard car valve on it. Failing that its knackered and you need a new one. Hope that helps someone in the future.

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