Pumped shower goes cold - turn off/on and it's warm again.

[andy6581]

Sorry for the lack of detail, as we have only just moved in. More detail to follow once i go back up in the loft, but wondering if anyone has any pointers ?

Issue :

The shower goes slowly cold. Turn off the shower for 5 secs (lets the pump stop). Turn on, and it;s fine for a short while. a 5 minute shower might mean 2 or 3 off/on cycles.

What i know so far:

Pump is a salamander in the loft

From the paperwork i have found, it has been in since 2006.

The shower is a thermostatic mixer

Can't imagine that either the cold header, or the hot water tank is running out, as i had a shower first thing this morning, and they will both have been full.

Hot water tank is on the first floor in an airing cupboard

hot water is fed to pump from an outlet on the side of the tank which i think is 28mm.

Hot water comes out of tank and then does a "U" shape before going up to the loft.

I can definitely notice a change in the noise from the pump (like it's struggling) when the water goes cold.

Any help greatly appreciated!!

Thanks

Andy

 

[HERTS P&D]

Is the pump a positive or negative head pump?

NEGATIVE HEAD PUMP.
http://www.ebay.co.uk/itm/Salamande..._Bathroom_Shower_Units_PP&hash=item519b598e34

POSITIVE HEAD PUMP
http://www.ebay.co.uk/itm/Salamande..._Bathroom_Shower_Units_PP&hash=item19c9aba1c3

Andy

 

[andy6581]

Is the pump a positive or negative head pump?

NEGATIVE HEAD PUMP.
http://www.ebay.co.uk/itm/Salamande..._Bathroom_Shower_Units_PP&hash=item519b598e34

POSITIVE HEAD PUMP
http://www.ebay.co.uk/itm/Salamande..._Bathroom_Shower_Units_PP&hash=item19c9aba1c3

Andy

Hi Andy

I will have to check tonight. Would it make a difference as the shower is below the cold water tank ?

Thanks

Andy

 

[HERTS P&D]

You also need to check that the cold water tank is not emptying out due to a faulty float valve.

Andy

 

[andy6581]

Thanks Andy

I will check all of the above tonight.

Andy

 

[andy6581]

Apologies, but after actually looking properly, and not just reading the salamander paperwork, it would appear that the salamander that was there has been replaced at some stage with one of these

http://www.diy.com/diy/jsp/bq/nav.j...mpid=4&tmad=c&ecamp=cse_go&CAWELAID=266877103

The cold water header is filling fine, and is absolutely huge.


Also, this is not much use, but I tried to capture the sound it makes. You can hear it change at 27 seconds in this video. This is when the shower starts to go cold

http://www.flickr.com/photos/66143073@N06/6254147265/in/photostream


Thanks

Andy

 

[andy6581]

A quick update on my situation, in case anyone finds this via search.

I've been managing the situation by ensuring that i timed the hot water a few hours before i generally use the shower. This has been woring ok, with only the occasional problems where someone wanted to have a shower at a random time . But with a new baby on the way, i have been concerned about the water temp, and the possibility of legionella if i let it go to low.

Hot water cylinder thermostat is set to 60 degrees. Tried to have a shower . The hot water had recently been on for an hour. I got spluttering, and the pump slowed. It was still pumping cold, but not much hot, so the shower went cold. Sometimes it just goes cold, other times it slows to a dribble. If i turned it off and on again it would burst a bit of hot through, and then quickly go off again. I can hear the pump noise change as it gets air in it.

I got my thermometer out and tested the water temp coming out of the hot tap, and it was at 65 degrees!. I'm now convinced that my thermostat wiring is faulty, preventing the cylinder 'overheating', and the fact that the water is too hot is causing air in the pump due to cavitation. http://en.wikipedia.org/wiki/Cavitation.

The pump manufacturer's website states that the water should not exceeed 60 degrees, because of exactly this.

I had a long shower in the morning - no issues! Tested the water temp, and it was 50 degrees at the tap!

Now to get my multimeter out