People Saying Heat Pumps are Rubbish - Are They?

benson1980

michaels said:

benson1980 said:

Alnat1 said:

grumpypensioner said:

Any one know what the temperature these new systems give you for hot water for showering, bath etc.? My old system is set for 55ºC which seems fine.

Heat pumps can normally heat the tank to around 52-55C. We have ours set to 47C once a day, plenty for our 2 showers and a bit of cleaning. It can be set up to keep reheating the water when the temperature drops below a set level, for those that use more. There's a boost option that uses the tanks immersion heater and can quickly reheat it if needed. This can also be used to take the temperature above what the heat pump can manage.

What you do need to be mindful of is that thermostatic shower valves will generally need a 10oC differential in temperature i.e. if HW supply from cylinder is 47 or 48, the max outlet temperature will be 37-38. The instructions for one of ours actually says that the HW supply needs to be 60oC (which is slightly ridiculous as stored water in the tank does not need to be this hot to provide sufficient warm water to a household). Outlet temp of 38 gives a comfortable warm shower.

We initially had our cylinder temp set at 45 but we had to turn it up to 48 as one of our showers really struggled with sufficient outlet temperatures, and this was on full adjustment.

Risk of legionnaires in domestic properties is negligible to non existent so we personally don't bother with the immersion cycle either. Just stays at 48. That does plenty of HW for 4, set at reheat during peak shower times.

How big is your cylinder?  Lets say you want a shower temp of 38C (probably more like 40) and cold water is 8c (can be les sin winter) then a 250l tank gives you about 340l of water so about 4 80l showers.

We have a 200 litre tank. Volume of stored hot water not a problem. The outlet temp at a thermostatic shower valve when the HW is set at a lower temp (which it typically is with ashps) does make a difference. As said 48 seems to be a good set point for us.

The point I’m trying to make is that most/all thermostatic shower valves seem to be designed for stored hot water at 55oC plus. 45 to 48 is actually fine for stored HW (particularly if you just set it to reheat at peak times), and we’d be ok if all of our showers were just standard mixer taps with a shower outlet. One of ours though did struggle to provide a comfortable shower until we turned it up to at least 48. Therefore nothing really to do with stored water capacity.

Alnat1

The tank's volume is generally decided by the size of the property. I believe the formula is something like 45l per bedroom + 45l, so it should be sufficient for maximum occupancy.

We are 2 people in a 4 bed house, 250l tank, so we can get away with heating the tank once a day to a fairly low temperature. Larger families or those who have lots of baths can ask for a larger tank than the formula requires or reheat water throughout the day.

There are plenty of options within the settings for users to adjust hot water to their needs.

Reed_Richards

benson1980 said:

What you do need to be mindful of is that thermostatic shower valves will generally need a 10oC differential in temperature i.e. if HW supply from cylinder is 47 or 48, the max outlet temperature will be 37-38. The instructions for one of ours actually says that the HW supply needs to be 60oC (which is slightly ridiculous as stored water in the tank does not need to be this hot to provide sufficient warm water to a household). Outlet temp of 38 gives a comfortable warm shower.

I know that the shower manufacturers themselves say that a temperature differential is necessary but I have seen this discussed elsewhere and everyone with practical experience reported then that it wasn't true.  Obviously manufacturers need to cover themselves against potential problems but this is one that rarely encountered.  If that was a problem with one of @benson1980's showers then I believe that is the exception rather than the rule

benson1980

Reed_Richards said:

benson1980 said:

What you do need to be mindful of is that thermostatic shower valves will generally need a 10oC differential in temperature i.e. if HW supply from cylinder is 47 or 48, the max outlet temperature will be 37-38. The instructions for one of ours actually says that the HW supply needs to be 60oC (which is slightly ridiculous as stored water in the tank does not need to be this hot to provide sufficient warm water to a household). Outlet temp of 38 gives a comfortable warm shower.

I know that the shower manufacturers themselves say that a temperature differential is necessary but I have seen this discussed elsewhere and everyone with practical experience reported then that it wasn't true.  Obviously manufacturers need to cover themselves against potential problems but this is one that rarely encountered.  If that was a problem with one of @benson1980's showers then I believe that is the exception rather than the rule

Maybe. We have a triton and a bristan one. So quite mainstream and neither were cheap. The triton one was fine, just about. Bristan one was too cold until we turned up the HW from 45 to 48.  Both sets of instructions specify your HW supply to the valve needs to be at least 55 (which it evidently doesn’t). Having just checked the triton specifies 55 and the Bristan specifies 60 which probably explains the above.

They just aren’t designed for slightly lower stored HW temps and the instructions confirm this. 

michaels

I guess they have a minimum proportion of cold water.

Ours seems to cope ok as the hot water runs out, just getting colder and colder, not sure how low the hot water can get before it no longer maintains 40c though

Reed_Richards

benson1980 said:

They just aren’t designed for slightly lower stored HW temps and the instructions confirm this. 

Precisely.  They are not designed for lower HW storage temperatures.  But they may work despite that and often do, it seems.   

Exiled_Tyke

My HW is set to 44 degrees which gets us through each day nicely (having heated up on cheap rate overnight).  I've never had a problem with the shower  (which is a Grohe) 

BoYaNY73

Inside my house! The « noise » reverberates all round my house. I can’t get away from it !

Spoonie_Turtle

BoYaNY73 said:

Inside my house! The « noise » reverberates all round my house. I can’t get away from it !

I believe you that there's a noise.  But since you're not in their home to know if they've changed anything else, can you be certain that it is definitely caused by something to do with the heat pump?

BoYaNY73

Would insulation all through my bungalow help to reduce the vibration from next doors ASHP system. They have their air con fans fixed to the adjoining walls