Shower Pump Cutting Out

[patchwork0815]

Hi folks, I've just moved from a flat to an older house, and there's a lot to wrap my head around regarding the plumbing, compared to the simple combi boiler in my old place.

I've got a vented cylinder fed from a cold water tank in the loft, and a positive head twin impeller shower pump fed from the cold water tank and the cylinder.

First (and most important) issue - the shower pump cuts out after about 10-15 minutes of use. No good for a longer shower or if two people want to shower in succession. I'm not sure if the cylinder is running out of water, or if the cold water pressure from the loft tank is too low to feed the pump and refill the cylinder at the same time. From testing the cold water tap in the bathroom with nothing else running, the pressure does seem to be pretty low.
One thing which might be important info - when the shower pump does cut off, I can still get plenty of hot and cold water from the bath taps.

Second - the hot water taps running off the cylinder feel scalding hot and measures at nearly 70⁰C, despite having the cylinder stat set to 45⁰C (I'm aware this should be higher for legionella reasons but for now I'm just testing). I know the water at the top of the cylinder is always going to be hotter, but this feels like a huge disparity. Is that normal?

Thanks in advance - I expect to be back here a lot with all the excitement and tribulations that come with buying a house from the 70s!

 

[Madrab]

What make/model of shower? Sounds like it might be overheating and the thermal cut-out is activating.

TBH, whilst it's not for me to dictate to anyone how long they should shower for, any more than 10mins in the shower is said to be bad for the skin.
The top of the cylinder will always be hotter than where the stat has been set - this is because the stat is on the bottom third of the cylinder so the water at top of the cylinder is hotter. There isn't usually that big a difference between set and actual though as you mention, Stat may need looked at.

 

[patchwork0815]

Thanks Madrab - I can't see anything that would indicate the make and model of the shower. It appears to be a non-thermostatic mixer shower - I just have two taps on the wall, one hot and one cold, and a fixed showerhead above.
The pump is an Aura AP238 2.0 bar twin impeller.

Any tips as to how I might figure out if the pump is hitting a thermal cutoff, without just replacing the whole thing?

While I can generally work with a <10 minute shower, it's nice to have the option, and it's a real pain when we can't have more than one shower consecutively.

The cylinder stat that was on there when I moved in seemed pretty old and dodgy, so I replaced it - a separate thermometer tested on the metal surface of the cylinder confirms that it's clicking off at roughly the right temperature.

 

[Madrab]

Aura AP238

Don't really recognise that as a shower pump. Have heard of Aura pumps before but not in a domestic application. Cant even find any reference to them or a manual.

Just check the pump when it cuts out, if you can't put your hand on it, it'll be overheating. It may also not be continuously rated which means it can't be used constantly and it will eventually cut out.

All in all, if you're new to the property then given there's no background to this pump nor any option for a manual or spares then may be an idea to start putting a budget together to replace it to more mainstream kit

 

[patchwork0815]

Much delayed update. The shower pump is not continuousluly rated, so that's the issue here.

Bought a new pump thinking I could just do a straight swap but failed to account for the difference in the layout of the connectors, so I can't get my pipework to line up Could start messing around with Hep2o or something but it's getting a bit beyond the level I'm comfortable with for now.

Anyway I've had a plumber in to assess the whole situation and have decided to rip it all out and get an unvented cylinder put in instead, solving the problem properly and paving the way for a future heat pump.