Heat Pump Pricing versus current costs

wrf12345

I see City Plumbing have the  Samsung Ehs 5Kw Heat Pump High Temp R290 Monobloc at £2500 inc delivery. This is air to water, a hot water cylinder is an extra grand but being into cold water showers something I would avoid. With just connecting to radiators this should be a relatively simple fit as long as you have an electrical connection and as the R90 is self-contained within the system should not need to be touched. Fitting and supplying it should be well within the £7500 grant if done professionally or free  fitting if done DIY as the existing run of radiators should work with the 65 degree output. Just one example of what is available against what companies are charging (15k gross locally).

Reed_Richards

It's good to see that the price of heat pumps is falling.

I think it is a big mistake to install a heat pump to run at 65 degrees for heating.  It's a false economy not to replace the radiators with ones having a suitably larger surface area if this is feasible.

Whilst you might not want hot water yourself, selling a house with no hot water might prove difficult.  As a buyer I would certainly ask for a few £k knocked off the asking price to cover the cost of a cylinder retrofit; or I might just look elsewhere.

wrf12345

On hot water, I already have electric showers but do not use them and electric on-demand heated water is a couple of hundred quid to fit, worth it to simplify the fitting of the heat pump so no real consequence on house price - and bear in mind that the central heating would only be run on the cheap time rates so any loss in COP is mitigated by half price electric rates made possible by not having lower temp heat pumps running constantly. Also, existing radiators were sized to mitigate a couple of huge bay windows facing north than have both been sized down (two-thirds of the glass gone) and an extra 50mm layer of celetox internal insulation on all walls except the south facing one, so the radiators are now oversized for the gas CH! But I am still pondering fitting individual air-air heat pumps, only the costly installation and no grant puts me off, as they would be a better fit for the way I live. As the central heating boiler is only four years old no great hurry.

matt_drummer

I don't think you fully understand low flow temperatures and heat pumps.

If you have the correct size heat pump for the property it will need to run constantly to deliver the heat necessary to maintain the temperature in the property.

The flow temperature required to deliver that heat is irrelevant to how long it needs to run, just how efficient it is.

Your 5Kw heat pump will only deliver a maximum of 5Kw of heat whether your flow temperature is 30c or 65c, you won't be able to get any more out of it.

If you need 5Kw of heat to maintain the temperature in the house then you won't be able to do that by running a 5Kw heat pump for only some of the day.



With the correct sized emitters low flow temperatures deliver the full heat output of the heat pump using less energy than that required at higher flow temperatures and undersized emitters.

What you are aiming to do is oversize the heat pump in the same way gas and oil boilers usually are.

You want to chuck loads of heat in at high flow temperatures using cheap rate electricity, that is not how heat pumps work, you'll need a much larger heat pump than necessary to do this and it will just cost more to buy, install and operate.

You also seem to underestimate the work required in swapping a gas boiler for a heat pump. There are lots of other things you need in addition to the heat pump and they all cost quite a lot of money.

I also very much doubt that you would qualify for a grant without fitting a hot water tank, I haven't  looked but I am pretty sure it is an MCS requirement.

In addition, no MCS registered installer is going to intentionally fit a grossly oversized heat pump so you can run it at excessive heat output for only part of the day. MCS and the grant process are designed to ensure appropriate and efficient installations, not fund free installations for clueless cheapskates.

The grant is awarded giving due consideration to the needs of future occupants of the property, not just the current owner/occupier.

FreeBear

wrf12345 said:

I see City Plumbing have the Samsung Ehs 5Kw Heat Pump High Temp R290 Monobloc at £2500 inc delivery. This is air to water, a hot water cylinder is an extra grand but being into cold water showers something I would avoid. With just connecting to radiators this should be a relatively simple fit as long as you have an electrical connection and as the R90 is self-contained within the system should not need to be touched. Fitting and supplying it should be well within the £7500 grant if done professionally or free; fitting if done DIY as the existing run of radiators should work with the 65 degree output. Just one example of what is available against what companies are charging (15k gross locally).

I suspect you still need a tank to act as a buffer - Heat pumps have a minimum water volume requirement (or at least the ones I've looked at). Not sure if the Heat Geek Combi Heat Store* would do the job - Even if it doesn't, it would take up a lot less space than a conventional DHW cylinder.

If you are doing a DIY install, you could go for a hybrid system - Retain the gas boiler for DHW and an extra boost when outside temperatures drop well below subzero. You wouldn't qualify for the £7500 grant with a hybrid system, but you wouldn't get it anyway with a DIY installation. But which ever route you go down, larger radiators are key to getting the best efficiency.

*) https://www.youtube.com/watch?v=a1XGBmBLUnA

matt_drummer

A traditional hot water tank for dhw cannot act as a buffer and doesn't add any volume to the heating system. The water inside the tank is heated by water flowing through a coil inside the tank. Even this coil cannot add any volume to the heating system.

Depending on the house, a volumiser may be required to get the required system volume and to aid with defrosting.

The Heat Geek combi store may work for adding system volume and to aid defrosting.

FreeBear

matt_drummer said:

A traditional hot water tank for dhw cannot act as a buffer and doesn't add any volume to the heating system.

I had in mind a combined DHW & buffer tank. For example - https://www.telford-group.com/product/tempest-heat-pump-indirect-30l-buffer

matt_drummer

FreeBear said:

matt_drummer said:

A traditional hot water tank for dhw cannot act as a buffer and doesn't add any volume to the heating system.

I had in mind a combined DHW & buffer tank. For example - https://www.telford-group.com/product/tempest-heat-pump-indirect-30l-buffer

Thank you for clarifying.

That is exactly what they are, two things in one case, a dhw tank and a buffer tank.

The dhw tank is still not adding any volume to the heating system.

wrf12345

Think you are over-complicating, here is a DIY installation - https://www.youtube.com/watch?v=9KG5X5EoJ7Q - itself more complicated than I would need as he is keeping the gas boiler and has the hot water cylinder in the system but does not seem beyond my ability with a bit more research. He's in Dublin and apparently you can't buy a heat pump unless there has been an official assessment signed off, which is not amusing.

matt_drummer

No.

It's really simple.

A heat pump that produces the heat you need at the lowest outdoor temperatures you experience and that has a wide range of modulation.

The biggest radiators required to run at around 30c flow temperature.

No zones, no buffer tanks, no low loss headers and no trvs.

Size all the radiators in the correct proportion to get the desired room temperatures based on accurate heat loss calculations.

Install accurate monitoring equipment.

Success is guaranteed.

High flow temperatures and unnecessary complications will result in an inefficient expensive to run set up.

Reed_Richards

FreeBear said:

matt_drummer said:

A traditional hot water tank for dhw cannot act as a buffer and doesn't add any volume to the heating system.

I had in mind a combined DHW & buffer tank. For example - https://www.telford-group.com/product/tempest-heat-pump-indirect-30l-buffer

I have something very similar but with hindsight I rather wish I didn't.  For a 4-port buffer to be most efficient you don't want the hotter flow water to mix with the colder return water.  Your best chance of achieving that is with a tall thin buffer tank to maintain stratification within the tank, with the hot pipes at the top and the cold pipes at the bottom.  The Telford buffer is fat and squat and all 4 pipes enter and leave at the same height so it looks as if you would get a lot of mixing between the flow and return water.  Or perhaps you are better off with a volumizer rather than a 4-port buffer.