Hotter heat pumps

[Mart]

Worth ensuring the most current tech is installed in this developing market?

Would not be happy to have a new install and its 20degC behind the leaders. Due diligence required.

https://www.bbc.co.uk/news/business-67511954

High temperature heat pumps are largely a marketing exercise to try to convince readers of the Mail that they can actually work. To be efficient the still need to operate at as low a temperature as possible.

The "high temperature" heat pumps they are talking about use R290 (propane) as the refrigerant. It's got advantages but it's not hugely better in performance than the other refrigerant that you're likely to come across, R32. Good R290 heat pumps perform better than R32 ones at low temperatures, less than 2C. Higher than that there's not much difference in performance, but there can be quite a difference in price.

My cheap R32 heat pump can operate up to 65C, more than high enough for most domestic heating purposes.

Good point, and I did check to see if the article covered it, which it does here:

Vaillant's aroTHERM plus heat pump works in outdoor temperatures as low as -20C and can supply hot water at up to 75C, though to remain efficient it is best not to exceed 55C, according to the manufacturer.

I'm interested in high temp HP's for two reasons. Firstly my house has 10mm microbore between the main pipes (28mm) and the rads, but the rads are all pretty large. Our gas consumption is pretty low, 6,400kWh last year (GCH + oven + DHW), but I'm not sure a conventional ASHP will work in the very worst conditions, perhaps 2 weeks, every other year. So it's an idea in the back of my mind, whilst expecting to run it at lower more efficient levels 99% of the time.

Secondly, my sister has a very large property, it's a home, business and smallholding. Following two large extensions (before they bought it) it's grown to about 2.25x the original build (late 1800's). It has a staircase at each end, and did have two oil boilers when they moved in, but now just the one, thanks to the work they've done.

But ...... they can't get the subsidy support for an ASHP, as the assesors don't believe it can get hot enough water to the extremes of the property. It's actually not as cold/leaky as I suspected, and with 10kWp of south facing PV to help contribute to heating and DHW through the year, I think an ASHP would be good. Again a HT unit might get them approval, even if the HT part is seldom needed.



[As an aside, does anyone have knowledge on polyurethane CWI? Their property is quite exposed, and they've been told that conventional CWI may not be suitable. I looked up polyurethane, and at first found nothing but negativity. But after a while the info seems to say that you need to use a good company who know what they are doing, otherwise it won't work well. But if done properly, it's fine, but about 2x the usual CWI cost. The front and one sidewall of the original building are still external, and solid no cavity, but some internal insulation on those, and I'd guestimate the external walls that are now internal, probably add 60-100tonnes of 'thermal mass' to help stabilise temps. External solid walls probably make up about 20% of the current external walls.]

[HML]

Bonded polystyrene beads seems to be the most recommended form of CWI. However, it does need to be properly installed, as all systems do.

[Fintray]

I hoped by posting this one up we'd catch some New Year HP customers while the money is still in pocket.

My deposit is paid and install is due in March (Vaillant aroTherm 10kW).

Exciting - how did you find a good company to install it - were there many to choose from in your area?

I asked a few local companies to quote based on the heat loss survey I carried out and that I would install the pipes and upgrade the radiators prior to the heat pump being installed. A couple of companies got back to me but only one actually came out and did a site survey, so based on the feedback on their website, the meeting during site survey and that they are a registered Vaillant advance installer convinced me to go with them.

[robl]

The foam CWI can be the best I think - certainly the most airtight. If done badly though it won’t set right as it needs the correct mix of two compounds, then there’s a risk of nasty chemical odours.

[Mart]

The foam CWI can be the best I think - certainly the most airtight. If done badly though it won’t set right as it needs the correct mix of two compounds, then there’s a risk of nasty chemical odours.

Many thanks. They had an assessor visit, and agreed for CWI, but when the installers arrived to put it in (polystyrene balls and glue), they refused saying the property was too exposed. I see their point, as the front (approx 16m long, or is it wide) faces slightly west of true south, so gets the strong winds, and is at the peak of a hill.

However, 'peak of a hill' is misleading, as they are about 60m above sea level, with the land only sloping very gently away to the south and north.

I'd heard of polyuretane insulation purely by accident when discussing wall tie issues a decade or so back, and one of the solutions (at least this is what I was told), was the polyurethane insulation, as it effectively glues the two walls together.

So I did the research and it's recommended for edge cases like exposed properties, and coastal properties (sister's property is about 3 miles from the coast), but many, many mentions that it has to be carried out by experienced workers.

The lack of CWI, impacts their ASHP assessments. Plus, it's just a good thing to do (if appropriate) for efficiency regardless of heating type. Hence my interest if anyone on here has some anecdotes for me.

[Countrypaul]

My parents had injected foam CWI put into the family house in the 1970s with very few problems up until the house was sold a year ago due to my father going into a home. The only problems I recall were wasps getting and trying to make a nest in the wall, and water getting into the cavity or rather onto the CWI when the roof developed a leak that caused a damp patch that dried up soon as the roof was fixed.

When we restored this house, the old cellulose CWI was lost due to the extensive changes (it had sagged below the windows and at the top of the walls).
We had PUR/PIR injected foam put into the cavities from inside about 7 years ago before plastering etc. and have seen no problems so far. Location: Wharfedale, Yorkshire