Balanced coverage?

[Tinbum]

I'm going to put heat pumps in my new house with underfloor heating. A neighbour down the road is totally rebuilding his house and his builder advised not putting one in. He's now had gas installed and a gas boiler.

I'm sorry but I really don't have much faith in installers at all. I've come across bad installers of many things and the annoying thing is they often just reply 'we've been doing it like that for years'!! Often the person having it installed is not knowledgable and doesn't know it's been done wrong.

[AE-NMidlands]

Another article:
https://www.theguardian.com/money/2021/ ... ng-outside (at-home-with-a-heat-pump-it-makes-hot-water-when-its-freezing-outside)

Sounds like an advert for Mitsubishi to me.

Haven't we seen people here saying "I went for the best, and it has paid off?" Maybe that was in the article. I got the impression though that their (M's) 2-stage machines were miles better than the opposition.
I take the point that most installers don't know what they are dealing with and will put in systems which can't hope to succeed, (apart fom by running the back-up resistive heating lots of the time.)

[Bugtownboy]

I'm going to put heat pumps in my new house with underfloor heating. A neighbour down the road is totally rebuilding his house and his builder advised not putting one in. He's now had gas installed and a gas boiler.

I'm sorry but I really don't have much faith in installers at all. I've come across bad installers of many things and the annoying thing is they often just reply 'we've been doing it like that for years'!! Often the person having it installed is not knowledgable and doesn't know it's been done wrong.

You have to have sufficient knowledge to challenge - not my mate down the pub knowledge, but real life.

Not wanting to blow smoke, but this is the value of a forum that relates experience, gives a view based on knowledge, and can give an unbiased (hopefully) view.

Our gas boiler is relatively new (6yr) with little use (2500 kWh/year). Although, philosophically, I should consider changing it, but I’ll sit back and wait and see.

[Ken]

People are too fixated on the DHW (domestic hot water)temp and are led in to making wrong decisions. The CH demand is the order of 10X that of the DHW and so if we are not careful tail is wagging dog. Running HPs to provide HOT 60C water destroys the COP and is plane stupid and dont even mention immersion heater back up to get it to 60C . STUPID

I think TS (thermal stores that pass mains pressure cold water through pipes in the HW tank) are the work of the devil. The reason being that by there design criteria you have to have a over large tank as in effect you can only use 60% of the volume of water energy before it becomes to low a temp. You then also have to heat the water to 60C+ in total, not just the top. So compared to a normal tank they have huge heat losses (2x from the tank size and 2X from the hot water )

KISS is the order of the day. For a start heat the water in the tank to the same LOW temp as the CH system say 35C to maintain good COP and then use a in line leccy heater to top up the temp to 40C as and when required.

When your HP is struggling in beast from the east moments you can disconnect the HW to allow the HP to concentrate on CH.

[Countrypaul]

I disagree with Ken about Thermal Stores, ours is a pipe through the TS to provide DHW but we never heat the whole tank to 60C. The ASHP is is used to heat the lower part of the store to around 35 and for most of the year we rely on an Eddi to heat the top of the store (approx 100L) to a higher temperature relying on excess PV, in the darker period of the year the Eddi is set to do this using the grid rather than excess PV. TMVs are used so that the supply of DHW from the TS is not too high (I have explained the use of TMVs we have elsewhere).


As the TS is within the themal envelope losses during the period when the CH is operational simply contribute to the house heating, and during the period when the CH is not in use the loss from the TS is effectively just from the top 100L so no different to a DHW tank given that the heat is provided by excess PV. The ASHP does not have a backup immersion heater.

During the warmer months the ASHP is normally off as CH is not needed it may come on if the temperature of the lower part of the tank gets below 25.

I don't yet have the Eddi turning on the ASHP when there is sufficient excess PV to make it worthwhile. During summer when this is likely to be the case it could heat the whole tank and I need to figure out how to adjust the settings to make best use of this.

We also have connections for Solar Thermal and a Wood burning stove boiler, but ST looks less likley to ever be implemented as more PV appears simpler and cheaper. The WBS is also questionable as the heat required for the house is less than expected, but would be useful as a backup in case of power cuts and we have a plentiful supply of wood.

[Ken]

Paul,
My comments were no where near aimed at you but for general Mr Average ( who does not have PV or diverter).

You seem to be doing as i suggested using the HP at low temp/high COP to do the heavy lifting up to 35C

Not sure how we can disagree about TS as that is written into British Standards for them ie to be able to provide 60% of the capacity of the tank based on 60C/65C? based on a full tank.

Like you my PV + diverter does all but 20-25 days a yr. The inline heater is a much cheaper option for those with out PV but wishing to maintain good COP on the HP. Have to say that my top heating tank does not really do baths except in summer.

==
Most older houses are not starting off from a good position when considering retro HP. Basically HPs are a long way off one way suits all as in boilers which anybody knows how to use. I would already have a HP by now if it was not for my small bore pipes and solid floor.

There is not enough knowledgeable experienced people around at the moment capable of tailoring their advice to the client. What does annoy me are those far too many customers who are given advice like needing bigger rads, then ignoring it and then complaining

Ken

[Bugtownboy]

This is sort of where I was coming from with my post. We are, I think, going to be sold an ASHP as a direct replacement for some form of FF boiler, usually gas, predominantly combi.

Forgetting the issues around emitters, ‘water’ tanks etc, most people will expect it to deliver the same performance.

Managing expectations now - by HMG - will stop the raft of Daily Fail/Express etc headlines about how rubbish they are.

From an environmental perspective, Heat Pumps have to deliver. It’s disappointing there’s not more information, sorry, honest informing of future users, what having a Heat Pump means.

As I said earlier, this forum is so valuable at understanding real world experience.