WATER QUESTION

[JIXAMAN]

I'v been doing the water in the van in stages... All the piping is JG 12mm with inserts and theres an accumulator just after the pump which is a 40psi 17 lpm. Ran the pipes for the sink, installed the sink, blanked off the cold feed that will go to the water heater (that I didnt have at that time) and the hot pipes that would eventually feed the sink hot. All worked fine. Pump worked with tap full open, pump short cycled on partial opening.

I got the water heater (instant hot water heater) and plumbed that in and plumbed in the shower and attached it to the blanked off part of the system, was well chuffed, all worked... For about a day then the pressure switch on the pump failed.

A bit of reading on forums and realised the current when switching isnt good for the pressure switches so got a new switch and set it up with a relay carrying the heavy work. Down side is the pressure switch is set at a factory value, which brings me here.

Should I be setting the pressure of the pump at the sink hot side as thats the farthest run (and at present the side that has the pump short cycling at round three second intervals, cold is not an issue) ? At present the pressure gauge shows 45 psi in the system fully charged with nothing running.

Is this a pump issue or a plumbing issue? Should I have went with 15mm pipe (reducing system pressure or should I still be looking to increase the pressure switch cutoff point?

Cheers...

 

[1 Cup]

Should the hot water be pressuerd, at all as its not tanked ?. Mines tanked and then pumped. To house hold taps at 65 degrees yours sounds like caravan taps ?
I turn my water on at the pump then turn the pumps back off

What hot water system is it. .?.

If its the £70.00 China gas burner ones that has 15mm pipe that runs shower head. not trusted
I run one from mains ie hose pipe , then just a cold tap pump . £ 10 submersible pump blue and white ones.from in a 25 ltr tank. but I don't put it in van as I thought it got to hot to hang on wall !.

 

[JIXAMAN]

To clarify, its not a submersible pump with microswitches on the taps, its a pressurised system... I turn on the pump, it pressurises the system (if required) and only switches on when a tap is open... Those in the know, know... Thanks anyway...

As for the water heater, yes its a Chinese on demand water heater (not the £70 dodgy one) and the pump delivers 40psi which is household mains pressure, the thread isnt about should / can you install one in a van, its about system pressure and pump setting, cheers...

 

[Nabsim]

If your pump is 40psi but pressure switch on heater showing 45psi something is not right, or is the 45psi a maximum setting?

Not sure what the pressure switch in question is actually for, I would assume there is more than one in the unit, a low pressure switch that would stop the unit firing if insufficient water going through then a higher pressure switch to cut everything if pressure is too great. Is that how your heater is set up?

 

[JIXAMAN]

I see your thinking, but ahll clarify, its probably me...

The pump is 40psi 17lpm... I replaced the pressure switch on the pump (nothing to do with the water heater), it was running at 28psi (on the pressure gauge plumbed into the system just after the accumulator) as the pressure switch I can only think was uncalibrated, as in a generic switch that fits a range of the manufacturers pumps. Using the pressure gauge I adjusted the pressure switch and the pump now kicks in at 38 and cuts out at 45 (thats what the pressure switch is for, turn on a tap, the accumulator starts the flow, when pressure drops the pump kicks in, when pressure reaches the limit it cuts out)... Ah take it my 40psi pump has a range too ah dunno but its not part of the issue unless someone can explain why but as said, pump runs at 45psi but only short cycles on the hot at the longest run...

Thanks anyway...

 

[merl]

I'v been doing the water in the van in stages... All the piping is JG 12mm with inserts and theres an accumulator just after the pump which is a 40psi 17 lpm. Ran the pipes for the sink, installed the sink, blanked off the cold feed that will go to the water heater (that I didnt have at that time) and the hot pipes that would eventually feed the sink hot. All worked fine. Pump worked with tap full open, pump short cycled on partial opening.

I got the water heater (instant hot water heater) and plumbed that in and plumbed in the shower and attached it to the blanked off part of the system, was well chuffed, all worked... For about a day then the pressure switch on the pump failed.

A bit of reading on forums and realised the current when switching isnt good for the pressure switches so got a new switch and set it up with a relay carrying the heavy work. Down side is the pressure switch is set at a factory value, which brings me here.

Should I be setting the pressure of the pump at the sink hot side as thats the farthest run (and at present the side that has the pump short cycling at round three second intervals, cold is not an issue) ? At present the pressure gauge shows 45 psi in the system fully charged with nothing running.

Is this a pump issue or a plumbing issue? Should I have went with 15mm pipe (reducing system pressure or should I still be looking to increase the pressure switch cutoff point?

Cheers...

Hmm, not sure exactly what it is that you're asking for advice about. What exactly isn't satisfactory now that you've replaced the pressure switch with a new pressure switch/relay combo?
Is the pressure switch adjustable? If not then I'm confused as to how you're attempting to "set the pressure".
The static pressure will be the same throughout the system so it doesn't matter where you take a measurement of static pressure, the pressure will vary at different distances from the pump/pressure vessel when the system is being used and water is flowing only.
Hope that helps?

 

[JIXAMAN]

Pump pressure switch is adjustable, thats how you set the cut in and out pressure, know that. Pump is short cycling, unsure if its a pump problem, as in is it too big for the setup or a system problem, as in is 12mm too restrictive for the pump... Thanks anyway...

 

[merl]

I see your thinking, but ahll clarify, its probably me...

The pump is 40psi 17lpm... I replaced the pressure switch on the pump (nothing to do with the water heater), it was running at 28psi (on the pressure gauge plumbed into the system just after the accumulator) as the pressure switch I can only think was uncalibrated, as in a generic switch that fits a range of the manufacturers pumps. Using the pressure gauge I adjusted the pressure switch and the pump now kicks in at 38 and cuts out at 45 (thats what the pressure switch is for, turn on a tap, the accumulator starts the flow, when pressure drops the pump kicks in, when pressure reaches the limit it cuts out)... Ah take it my 40psi pump has a range too ah dunno but its not part of the issue unless someone can explain why but as said, pump runs at 45psi but only short cycles on the hot at the longest run...

Thanks anyway...

When the pump runs it shifts a fixed amount of water per minute, let's say 5 litres per min for instance. If you open a tap and let 5 litres per min or more flow from that tap then the pump will run 100% of the time in an attempt to bring the system back up to pressure and turn the pressure switch off. It will never be able to achieve this until you close the tap.
If you open a tap that doesn't pass 5 l/sec, let's say it only passes 1/2 of that and just 2.5 l/sec then the pump MUST short cycle at a half on half off (called a 50% duty cycle), if it didn't the excess water wouldn't have anywhere to go.
Your expansion vessel/accumulator will only prevent the short cycling IF the output capacity of the pump is less than the draw off rate but opperating time under these conditions is limited because eventually you lose virtually all pressure in the accumulator.
So unless I've misunderstood your system is working fine. Larger bore pipes would get you a better water flow for sure but that's all and in a MH fast flow isn't usually a priority.

 

[Thistle]

@JIXAMAN
If you have an expansion vessel correctly pressurised you really shouldn't be getting any rapid pump cycling at low flow rates
An Instantaneous water heater probably won't like that at all.

I have a 5L expansion vessel in my current van due to the maths suggesting that was the size required for my 30L Calorifier!

However here is the smaller expansion vessel I used with an instantaneous water heater in my other van:

 

[merl]

@JIXAMAN
If you have an expansion vessel correctly pressurised you really shouldn't be getting any rapid pump cycling at low flow rates
An Instantaneous water heater probably won't like that at all.

I have a 5L expansion vessel in my current van due to the maths suggesting that was the size required for my 30L Calorifier!

However here is the smaller expansion vessel I used with an instantaneous water heater in my other van:

The hysteresis of the pump switch will ultimately determine cycling but I don't know of any single pump switch where you can set upper AND lower pressure limits, I guess that's just pot luck, if you wanted to faff with that sort of thing you'd have to delve into 2 separate switches. As I said the amount of cycling will largely depend upon the delivery rate of the pump vs the system flow, and the size of the vessel it's self to some degree.
I really wouldn't expect an instantaneous water heater to be bothered by the pump cycling because ultimately the system pressure will be stabilised by the expansion vessel, after all that's what it's there for.

 

[Nabsim]

A lot of the instant water heaters have a maximum pressure stated, the one I was looking at was 30psi I think. If your is like this you will need to fit a reducer before the heater to drop the pressure to what is safe for the boiler.