Unusual Shower Pump Problems when Using Oil Boiler

[JoseSpring]

Hi,

I have an unusual issue with my shower pump:-

Last year I had a thermostatic shower with a twin pump fitted.
Since it was installed the shower has worked intermittently. Sometimes it's fine, other times the water pulses and loses power over a few minutes. Turning the shower off and on again (with the tap) restores the full flow for a few more minutes before it needs doing again.

The water is heated with an oil boiler. I believe it is a gravity boiler (for the simple reason that there is no cylinder thermostat).

Then in the spring I switched the boiler off and started using the tank's immersion heater. And the problems went away overnight.

Now I've tried the boiler again and immediately the issues have returned, only worse than before! Now the pump works and gives a strong flow of water, but it's all cold, even though there is hot water in the tank.

Temporarily I've switched back to the immersion heater, but I'd like to get this sorted before I need the central heating...

Thoughts
Could the hot water be too hot when heated by the boiler? I believe this can cause cavitation in the pump. Might it stop the hot water coming through at all? The only adjustment I can see on the boiler is a simple "hi/low" dial. I've set this to low, but it's not helping.
A local heating engineer has said he can fit a valve that limits the flow of water to the hot water tank when it reaches a pre-set temperature. Seems a bit steep though - £600 (including new room thermostat and timer).
Could the boiler thermostat need calibrating?
Am I barking up the wrong tree? Any other ideas what the problem might be?

I'm getting desperate (and the weather's getting colder)!

Thanks in advance for your ideas..

 

[WDIK]

is the cold mains feed?

 

[ajstoneservices]

Failed boiler stat could be the cause, how hot is the cylinder when heated by the boiler.Rads also too hot to touch when stat on low?.

 

[JoseSpring]

Thanks for your help/interest. As you can see, I'm a novice in this area, but learning more daily! I'm worried that a a little knowledge is a dangerous thing, so really appreciate your expertise!

is the cold mains feed?

I believe so. The hot water tank is fed from a feeder tank in the loft. Does this mean anything?

Failed boiler stat could be the cause, how hot is the cylinder when heated by the boiler.Rads also too hot to touch when stat on low?.

I don't have any specialist equipment, but I guess one way to find the boiler temp is to check the temp of the water from a hot tap? I'm off to Boots to grab a thermometer.

 

[kevplumb]

A local heating engineer has said he can fit a valve that limits the flow of water to the hot water tank when it reaches a pre-set temperature.

View media item 15486

 

[JoseSpring]

^^ is that what he'd charge me £600 to fit?!?

Any idea why he said I'd need a new room thermostat and boiler timer too?

 

[kevplumb]

y plan

• kevplumb
• 19 Sep 2009
• 22

prob gonna fit a "y" plan

 

[bathstyle]

It sounds like the shower pump hose might be deforming when the Hot water is passing through it causing low flow. Whatever happens, the water should not exceed 60 degrees