Water Pump and Pressure Release Valve on Calorifier

[JonoSlatter]

Hi all,

I’m getting a rapid on/off rattling from the pressure relief valve (PRV) on the calorifier on my 336 – see video below.
Youtube

The water pump is a Shurflo 2901-0213, probably around 10 years old.

It started with the PRV briefly opening and shutting every minute or so, with the pump kicking in for a second each time. Now, as soon as I turn the water system on, the PRV rattles continuously and discharges a significant amount of water.

What I’ve tried so far:

• Adjusted the pump pressure (full range) – no change
• Replaced the PRV (now on my third 3-bar valve) – no change

So I’m wondering:

• Could the pump be the issue (pressure spikes or failing pressure switch)?
• Or is there something else I should be checking?

Any ideas much appreciated.

Thanks,
Jonathan

 

[PaulRainbow]

Pressure switch would be a strong suspect.

 

[JonoSlatter]

Pressure switch would be a strong suspect.

Thanks Paul. Think you are right. So far not managed to find a spare part Pressurre Switch for the Shurflo 2901 0213 so it may need to be a new pump

 

[PaulRainbow]

Thanks Paul. Think you are right. So far not managed to find a spare part Pressurre Switch for the Shurflo 2901 0213 so it may need to be a new pump

Double check, but i think it's this one: Pentair SHURflo 94-706-00 30PSI Pump Switch Aqua King 2900 Junior

Parts for Shurflo Pump model # 2901-0213

 

[JonoSlatter]

Thank you I will take the current one out and have a look. Thank you for passing that on

 

[Dockhead]

I find those microswitches to be quite unreliable in this application. I don't know about the ShurFlo, but Johnson pumps use a generic microswitch which you can buy for £2 from Mouser. The part number is stenciled on it, which you can look up in Mouser or one of the other electrical supply platforms. When I was still using them, I kept a bag of those microswitches in my pump spares box.

You can greatly extend the life of them by fitting a flyback diode to absorb the inductive voltage spike which occurs when a DC motor is switched off. Some people fit relays as well.

But the gold standard is to fit a separate heavy duty well pump switch, like a Square D. Something like this: Square D 9013FSG2J20 Water Pump Pressure Switch, 20/40 PSI : Amazon.co.uk: Business, Industry & Science

If you stick with the microswitch, I'd use something like a MBR1065 Schottky diode. Wire it directly across the pump terminals, cathode to positive, and anode to negative. A TVS diode would be somewhat better, but probably overkill for this application.