New ASHP Installed & Showers Running Cold

Grannysan

We've recently had a new ASHP system installed.  Sadly, following installation, we've been told that our underfloor heating is "the wrong type" & won't work properly with the new system.  And neither will our showers, apparently; a plumber who visited because our showers are all running cold, said that it's because they're not designed to run with the new system & the hot water supply is being overwhelmed by the cold water mains input.  

His only solution was to turn the hot water cylinder temp up to 55C, which still results in only lukewarm showers. 

What's worse, is that he visited on a day when our mains water pressure was much reduced because of a broken main somewhere nearby.  So once that is fixed, I suspect that our showers will run cold again, despite the increased cylinder temp?

Sorry for the long post - but can anyone help with advice?  Do we need to replace all our shower controls to "fit in with" the new system? (They're nearly 20 years old).  I'm sick of having cold showers since our ASHP was installed & hubby isn't willing to retile everything....

Netexporter

Did they fit a new hot water cylinder as part of the installation? 

Reed_Richards

There are two types of showers that I can think of, ones that are fed from the bath taps so you adjust these to get the temperature you want then switch from bath to shower.  But if somebody flushes a toilet nearby, that can cut the flow of cold water so the shower can become scaldingly hot, which is a bit dangerous.  The other type uses a thermostatic mixer valve so this doesn't happen.  Which type do you have?

Either way, you should have got a new hot water cylinder that is unvented and pressurised so it should be easy to balance the hot and cold water flow rates to give you the temperature you want.

With a heat pump you typically heat the water in your cylinder to somewhere between 40 C and 55 C.  If it was set to 40 C you would not need that much cold water to balance with the hot when taking a shower but I still find it hard to understand what is going wrong unless you didn't get a new pressurised hot water cylinder, which would be very unusual, almost unheard of.

As for your underfloor heating, the two basic types either use heating water pipes under the floor or heating wires under the floor.  If it's wires then a heat pump makes no difference but that must have been known from the outset.  If it's water pipes under the floor then they might have been spaced quite wide apart so the need hotter water but they should still work.

I'm wondering how on earth you got your ASHP.  You are complaining about issues that should never have been allowed to happen so something has gone badly wrong.  Was it a self-install?

By the way, there is a special section of the forum reserved for questions about heat pumps.  You might find your question gets moved there by the admins.    



    

Keep_pedalling

More details required, what water tank do you have? Has the ASHP replaced a gas boiler with no other upgrades?

If you have wet underfloor heating I don’t see how it can be the wrong type.

matelodave

As said above, many more details are needed about your water tank (vented or unvented), heatpump type and size, shower mixer and underfloor heating set up etc. What controls have you got and how are they set. When was it installed and by whom. Did you have the system installed or was it done by your landlord etc. as that may have a bearing on how well it was specified and who to address about your problems.

If you just had a heat pump bunged on in place of a gas or oil boiler without the system being assessed and, if necessary modified to suit a heat pump, then its not surprising that it isn't working as it should.

Most showers don't perform everso well if the hot water is fed from an vented tank and the water is from the mains unless they are designed for unbalanced supplies or the supply pressures have been balanced. Likewise the hot water tank should be suitable for use with a heat pump - the internal coils are designed to work with lower flow temperatures

We have a heat pump, wet underfloor heating and an unvented hot water tank that delivers water to our shower mixer at around 45 degrees and we have no problems.

note, corrected to vented tank

born_again

Grannysan said:

We've recently had a new ASHP system installed.  Sadly, following installation, we've been told that our underfloor heating is "the wrong type" & won't work properly with the new system.  And neither will our showers, apparently; a plumber who visited because our showers are all running cold, said that it's because they're not designed to run with the new system & the hot water supply is being overwhelmed by the cold water mains input.  

His only solution was to turn the hot water cylinder temp up to 55C, which still results in only lukewarm showers. 

What's worse, is that he visited on a day when our mains water pressure was much reduced because of a broken main somewhere nearby.  So once that is fixed, I suspect that our showers will run cold again, despite the increased cylinder temp?

Sorry for the long post - but can anyone help with advice?  Do we need to replace all our shower controls to "fit in with" the new system? (They're nearly 20 years old).  I'm sick of having cold showers since our ASHP was installed & hubby isn't willing to retile everything....

Call the installers back. This is for them to sort as per consumer regulations. As they should have advised you of this both pre & during install.

FreeBear

matelodave said: Most showers don't perform everso well if the hot water is fed from an unvented tank and the water is from the mains unless they are designed for unbalanced supplies or the supply pressures have been balanced.

I suspect you meant to say vented tank - A vented DHW cylinder with a header tank in the loft would work with a shower if a booster pump was plumbed in. But I would expect a newly installed heat pump would have an equally new unvented cylinder so hot & cold water pressures would be the same.

matelodave

FreeBear said:

matelodave said: Most showers don't perform everso well if the hot water is fed from an unvented tank and the water is from the mains unless they are designed for unbalanced supplies or the supply pressures have been balanced.

I suspect you meant to say vented tank - A vented DHW cylinder with a header tank in the loft would work with a shower if a booster pump was plumbed in. But I would expect a newly installed heat pump would have an equally new unvented cylinder so hot & cold water pressures would be the same.

thanks for that, I've now corrected it