Calorifier Help!

[Botski]

I've got a problem with the calorifier relief valve lifting.

 

I also have a Rinnai LPG instantaneous water heater with a 3 way valve to change from engine heat when cruising to LPG when moored for a while.

 

Recently the calorifier relief valve lifts when we select and fire the LPG boiler.

 

If I switch off the hot water pump the relief valve seats.

 

Could I have an internal leak on the calorifier?

 

Any advice would be gratefully received.

 

Make the most this weather!

 

Botski.

 

 

[Paul C]

What role does the hot water pump do? I thought that the (cold, normal) water pump was sufficient, because as you draw hot water out of either a calorifier or instant gas water heater, the water pump fed it into its cold inlet?

[Botski]

Thanks for looking at my thread.

 

The boat has 2 domestic water pumps. One for the hot water system and one for the cold water taps.

 

Not sure why. It was like this when I bought the boat. Its a Piper 53 ft

[Jigsawged]

I recently had a similar problem which was corrected by changing to 30psi pump for a 20 psi. No further probs. do you know your pump ratings?

[Botski]

I'm not sure of the rating but one of them is easy to adjust the cut in pressure but the other one 'shureflow' is not so easy.

 

What concerns me is that we have just come back from 10 weeks up the Shroppie and there abouts with no problems at all. This has started since we got back on the mooring.

[Guest]

Is the hot water pump a pressurising pump, or a circulating pump for the heating system? Seems odd to have a second pump for the hot water system, though there could be a reason for it. Is there no expansion vessel on the hot water system and if so is it set to the correct pressure? My hot water system dribbled constantly via the PRV until I fitted on of these vessels (good price on Ebay, but don'tuse the central heating type!) Not sure why it would suddenly start doing this, but perhaps the PRV has gone weak/got scaled up? They are not very robust in my experience.

[Botski]

Yes I agree its odd to have 2 pumps. They had a common suction from the water tank but I split them into 2 separate suctions and they work the hot and cold water systems independently. One is a Jabsco pump the other is a shureflo.

 

The central heating circulating pump is quite separate and has no connection with the domestic water system. There is an expansion tank on the central heating system but nothing on the domestic hot water side.

 

When the PRV lifts it sounds like a machine gun and sprays water a good six inches out of the outlet on the hull.

[Tony Brooks]

Yes I agree its odd to have 2 pumps. They had a common suction from the water tank but I split them into 2 separate suctions and they work the hot and cold water systems independently. One is a Jabsco pump the other is a shureflo.

 

The central heating circulating pump is quite separate and has no connection with the domestic water system. There is an expansion tank on the central heating system but nothing on the domestic hot water side.

 

When the PRV lifts it sounds like a machine gun and sprays water a good six inches out of the outlet on the hull.

 

If the pump cut out pressure is very close to the PRV settings then the pressure pulses that can cause water hammer can also jump the PRV up and down. From this I deduce that your instant gas water heater's diaphragm chamber may be acting as a damper that stops this - as an accumulator might. However I suspect you may have a failing pressure switch in the pump. :Possibly dirt in the switch diaphragm chamber or a partial blockage in the drilling supplying the chamber (actually a nearly closed drilling).

 

My answer would be an external, adjustable pressure switch and since Square D switches seemed to have disappeared, controlling the pump via a relay - or a new pump/try to adjust the old one.

[Grebe]

Give the PRV a good twist or remove it and give it a good clean and see how things are then.

 

With regards to Square D. I think they stopped trading about 7 or 8 years ago.

 

When I worked on the railway ( six years into retirement now) there were lots of Squared D relays in use. To continue using Square D, Unipart Rail bought the IP rights to Squared D relays and built and serviced them at York for their own use.

 

Could they also have the IP for Squared D pressure switches?

[Paul C]

It could be a dodgy PRV - they do fail every now and again. I had a PRV fail and bought one from eBay with a pressure gauge in it, for £10.49 inc.

[Botski]

A sincere thank you to everyone who has assisted me with this problem. A typical response from the cut.

 

I'll have a good look at the PRV and the pump cut out settings and it that doesn't sort it I'll be back!

[Botski]

I think I have bottomed this problem once again thanks everybody.

 

I am pretty certain it is the pressure switch in the hot water pump, A Johnson WPS 29 10-1340-11. It looks like the micro switch has failed.

 

Very easy to fix but expensive through Johnson pumps or anyone else. The exact same micro switch is for sale in Maplins for £2.49 inc vat

 

It is part No GW71N Std Micro switch on the Maplins web site.

 

If you have the same pump problem but are not sure how to tackle it get in touch and I'll talk you through how I did it.

[smileypete]

If a bog standard auto relay from the likes of Halfords/Ebay/motor factors, is put between pressure switch and pump motor, it'll greatly prolong the electrical life of the pressure switch and avoid these sorts of problems.

 

cheers, Pete.

~smpt~

Edited July 8, 2013 by smileypete