Calorifier PRV

[Caladh]

I have a calorifier which appears to be leaking from the valve pictured. The little lever goes round horizontally and I am loathed to operate it vertically if it will even do that, for fear or breaking it or it not sealing. Does anyone else have something similar and could advise whether a replacement may be available or even if it is serviceable? Malo 39 from 1996. The lower pictured hose is the inlet to the calorifier and the upper house where the lever is, is I believe the drain - which isn't draining!!

 

[VicS]

Calorifier PRV

PRV ??????

or combined inlet fitting with drain cock ?

 

[Caladh]

Th manual for the calorifier suggests it's a PRV. It seems to weep once the water heats up.

 

[pvb]

View attachment 77685

I have a calorifier which appears to be leaking from the valve pictured. The little lever goes round horizontally and I am loathed to operate it vertically if it will even do that, for fear or breaking it or it not sealing. Does anyone else have something similar and could advise whether a replacement may be available or even if it is serviceable? Malo 39 from 1996. The lower pictured hose is the inlet to the calorifier and the upper house where the lever is, is I believe the drain - which isn't draining!!

After a quarter of a century, it doesn't owe you much so I wouldn't bother trying to service it, and a replacement is certainly available. It's actually a combination non-return valve and PRV. Here's just one possible replacement - https://www.yachtboatparts.com/40-bar-sigmar-pressure-relief-non-return-valve-12inch-8193-p.asp

 

[jwilson]

Probably replace. It needs to be one that operates at slightly higher pressure (bar) than your water pump pressure, but below what will burst the tank or pipes.

 

[PCUK]

If you don't have an accumulator tank any PRV will open when the water heats up.

 

[VicS]

If you don't have an accumulator tank any PRV will open when the water heats up.

It's an expansion tank you need to prevent the PRV opening when the water heats up.

The accumulator tank is on the cold water system to smooth out pressure fluctuations which can cause rapid on/ off cycling of the pump

but with an NRV directly on the on the inlet to the calorifier an expansion tank will be difficult to fit unless it can be fitted on the calorifier outlet.

 

[johnalison]

I don't know about Malos but my HR uses a non-standard valve that incorporates a one-way valve and a replacement had to be sourced from Italy. It might be worth checking before using any old PRV. A problem I had was that the thread didn't match exactly with the result that the piping had to be changed a bit.

 

[pvb]

If you don't have an accumulator tank any PRV will open when the water heats up.

Like many posts, this isn't true. I don't have an accumulator/expansion tank, and don't get any water leaking from the PRV. This may be because the volume of piping to the sink/basin/shower is sufficient to absorb expansion.

 

[Turnnidge]

As johnalison says, it looks like the Sigmar ones that HR use, it is worth talking to Transworld Yachts at Hamble Point, as that is where I got one last year for about £40. It is a PRV and NRV in one, so make sure you not the arrow on the side!

 

[pvb]

As johnalison says, it looks like the Sigmar ones that HR use, it is worth talking to Transworld Yachts at Hamble Point, as that is where I got one last year for about £40. It is a PRV and NRV in one, so make sure you not the arrow on the side!

The one I linked to in post 4 is suitable for Sigmar calorifiers and is about half the price you suggested.

 

[westhinder]

I had the same problem with a different type of PRV.
Trying to resuscitate the old PRV is not worth the trouble. Replace it and take care you get a good leak-free system and forget about it.

 

[neil1967]

It's an expansion tank you need to prevent the PRV opening when the water heats up.

The accumulator tank is on the cold water system to smooth out pressure fluctuations which can cause rapid on/ off cycling of the pump

but with an NRV directly on the on the inlet to the calorifier an expansion tank will be difficult to fit unless it can be fitted on the calorifier outlet.

Does it actually matter which side of the calorifier the expansion tank is fitted? I had always assumed that it would be fitted after the calorifier, after the mixer valve (if fitted).

 

[VicS]

Does it actually matter which side of the calorifier the expansion tank is fitted? I had always assumed that it would be fitted after the calorifier, after the mixer valve (if fitted).

No I dont think it does. I wondered about connecting it to the hot water system but they are suitable for use up to 90C .

 

[PaulRainbow]

Does it actually matter which side of the calorifier the expansion tank is fitted? I had always assumed that it would be fitted after the calorifier, after the mixer valve (if fitted).

Depends if there is a non-return valve and where it's located. If the expansion tank was fitted to the calorifier inlet it would need to be after the NRV, as it is in the drawing Vic posted. However, most modern calorifiers have the NRV fitted directly to the tank, so the expansion tank would need to be fitted after the calorifier, this is the more common place.

 

[Caladh]

Thanks to all for the valuable info.

 

[PCUK]

It's an expansion tank you need to prevent the PRV opening when the water heats up.

The accumulator tank is on the cold water system to smooth out pressure fluctuations which can cause rapid on/ off cycling of the pump

but with an NRV directly on the on the inlet to the calorifier an expansion tank will be difficult to fit unless it can be fitted on the calorifier outlet.

They actually do the same job, in fact both jobs.

 

[VicS]

They actually do the same job, in fact both jobs.

The NRV in the cold feed to the calorifier prevents both the expansion tank doing the job of the accumulator and the accumulator doing the job of the expansion tank.

Omit the NRV , and they will, but you may get some warm water from the cold water taps.

 

[[3889]]

Found this thread as I have a similar problem to the OP on a new-to-me 2016 boat. As there is no expansion tank in the system fitting one will hopefully solve the problem.
Before I do can anyone clarify why the PRV/ drain continues to leak long after the water has been heated? Surely expansion should then cease and the leak stop? Or could it be another issue?

 

[VicS]

Found this thread as I have a similar problem to the OP on a new-to-me 2016 boat. As there is no expansion tank in the system fitting one will hopefully solve the problem.
Before I do can anyone clarify why the PRV/ drain continues to leak long after the water has been heated? Surely expansion should then cease and the leak stop? Or could it be another issue?

Maybe defective / worn out and not reseating properly. They are really only intended to open occasionally / in an emergency if the calorifier becomes over pressurised due to some other cause..

Is it a combined pressure and temperature relief valve that could be opening on temperature rather than pressure?