Hotpot problem

[Siftasam]

Please can anyone throw light on our ongoing problem with the Hotpot calorifier pressure relief valve.

First problem was the prv constantly releasing when jabsco pump pumped to pressure 1.41bar.
Spent days searching for problem then discovered that there is a check valve at the tank inlet fitted by Hotpot. This was a problem as our expansion tank is in the cold waler line before the calorifier.
Hotpot require the ET to be fitted in the HOT water line where it exits the tank.

After much aggravation re-routing/replacing pipework we bled the system.
Alas. Although there was less water released, the prv continued to drip as soon as the jabsco pumped to pressure. Changed prv in case faulty. No difference.
Also for the first time in 30 years the pump blew a fuse !

Has anyone a solution please. We are at a loss as to where to go next. Has anyone removed the check valve , together with the cold water pipework fitted on the tank (designed to reduce the water temperature I understand). ? Thiis would replicate the set up with our original tank-one line in (cold) and one line out (hot).
All suggestions gratefully received !

Sorry everyone…just re-read original posts and help you all gave re new purchase. So..asap hotpot has no nrv. Think I shall try replumbing it as per the original tank and cross fingers and toes.
However, still do not understand why pressure relief valve will not hold….

 

[Plum]

Please can anyone throw light on our ongoing problem with the Hotpot calorifier pressure relief valve.

First problem was the prv constantly releasing when jabsco pump pumped to pressure 1.41bar.
Spent days searching for problem then discovered that there is a check valve at the tank inlet fitted by Hotpot. This was a problem as our expansion tank is in the cold waler line before the calorifier.
Hotpot require the ET to be fitted in the HOT water line where it exits the tank.

After much aggravation re-routing/replacing pipework we bled the system.
Alas. Although there was less water released, the prv continued to drip as soon as the jabsco pumped to pressure. Changed prv in case faulty. No difference.
Also for the first time in 30 years the pump blew a fuse !

Has anyone a solution please. We are at a loss as to where to go next. Has anyone removed the check valve , together with the cold water pipework fitted on the tank (designed to reduce the water temperature I understand). ? Thiis would replicate the set up with our original tank-one line in (cold) and one line out (hot).
All suggestions gratefully received !

Sorry everyone…just re-read original posts and help you all gave re new purchase. So..asap hotpot has no nrv. Think I shall try replumbing it as per the original tank and cross fingers and toes.
However, still do not understand why pressure relief valve will not hold….

You must have a non return valve where the fresh water goes into the calorifier. This ensures pressure increases in the calorifier due to expansion as the water heats up do not over prssure your pump and possibly damage it. You may also have a thermostatic mixer valve to regulate the temperature of the water coming out of the calorifier. The tank fitted to the inlet fresh water pipe after the pump and before the non return valve, is an accumulator tank (not an expansion tank) to reduce rapid cycling of the water pump. In addition, an expansion tank is sometimes fitted after the non return valve or in the hot water outlet pipe to absorb some of the expansion due to heating of the water. Without an expansion tank you will most certainly get some leakage from the pressure releif valve as the water heats up. See Google Image Result for https://heatmyboat.co.uk/wp-content/uploads/2016/12/Calorifier-installation-diagram.jpg

Www.solocoastalsailing.co.uk

 

[Siftasam]

Hello Plum. Thanks for your reply. Greatly appreciated.
We had our Isotemp calorifier for 30 years before lack of availability re new immersion unit put paid to it.
The original set up : pump-accumulator-cold waterside of mixer taps-calorifier-hot side of mixer taps. No non-return valve, no expansion tank. No problems in 30 years! Yes, we had a little warm water coming from the cold water taps initially on turning them on but no big deal. The excess pressure was taken up by the accumulator which Jabsco advised it was capable of absorbing and not a problem..
Had the initial warm water been unacceptable they advised , as you say, an NR valve in the cold supply and an expansion tank.

Since fitting the Hotpot which we thought, incorrectly as it turns out, had a non-return incorporated in the unit we fitted an expansion tank into the hot water side. This inevitably made a tangle of water pipes running hither and thither.

On learning that the Hotpot did NOT in fact have an NR valve the expansion tank becomes redundant. So we are now removing it from the hotwater feed and reverting to our original (much tidier !) set up.
Fingers crossed.
Sifasam

 

[ithet]

A friend had a problem with prv letting out water. Online research suggested it could be a failed pressure sensor in the Jabsco water pump causing it to over pressure. Replacing the pump solved his problem.

 

[Siftasam]

Ithet- thank you for your input. Fantastic !…we dismantled the Jabsco to discover the pulsation dampers completely useless and virtually turned inside out. We presume that the pressure switch, as you say, has been over pressuring the system.
We have replaced the pump and now, hurrah, no problem.
Thanks so much.

 

[neilf39]

Have you checked the pressure of the accumulator (no nrv) or expansion tank (nrv). If it's too low it won't absorb the pressure of the hot water expansion as the bladder is already extended. Also if it's too high and prv operates first. I think it should be just above the cut in pressure of the water pump.

 

[ithet]

Ithet- thank you for your input. Fantastic !…we dismantled the Jabsco to discover the pulsation dampers completely useless and virtually turned inside out. We presume that the pressure switch, as you say, has been over pressuring the system.
We have replaced the pump and now, hurrah, no problem.
Thanks so much.

You are very welcome.