York Heatpumps - any experience?

[JohnMo]

17 minutes ago, DanDee said:

 

It would actually be the perfect in room buffer, for the spring/autumn seasons.

Why - what's the theory that makes you think that?

[JohnMo]

13 minutes ago, DanDee said:

be controlled as a boiler, on a fixed low flow temp? This part of the automation seems to work great only when the output/requirement can match, for the rest of the time it just starts and stops every 5(random number) minutes

Doesn't it do that already, mine has a min flow temp for heating of 25 deg. A lot of the time I would need less temp than this so for some of the year I am on a fixed flow temp.

 

If you heat pump runs for less than 10.minutes you do not have enough water engaged, you either have too many zones or one that too small. Or if you want lots of zones you need a buffer if you already have one a bigger one.

[DanDee]

7 minutes ago, JohnMo said:

Why - what's the theory that makes you think that?

"First heat cycle will be good as a ready source to a sorb heat, but once heated, it just a radiator what goes in comes out"

 

Because of the extra volume of water+iron that you would have in each room, if the requirement is low you gain a few hundreds of watts buffer on the whole system, as that water+iron looses the heat into the room. But as you mention running with 25C maybe the benefit is minimal/pointless.

 

[JohnMo]

2 minutes ago, DanDee said:

Because of the extra volume of water+iron that you would have in each room, if the requirement is low you gain a few hundreds of watts buffer on the whole system

Makes sense, adding system volume with a large water capacity radiator 

[DanDee]

15 minutes ago, JohnMo said:

Doesn't it do that already, mine has a min flow temp for heating of 25 deg. A lot of the time I would need less temp than this so for some of the year I am on a fixed flow temp.

 

If you heat pump runs for less than 10.minutes you do not have enough water engaged, you either have too many zones or one that too small. Or if you want lots of zones you need a buffer if you already have one a bigger one.

Some do like your case some not. I said 5 minutes, but 10 or 15-20 minutes cycles are still too often for a whole year.

[JohnMo]

Do you need your heating on when it's 16 degs outside? That's when the heat pump struggles to get rid of the heat.

[DanDee]

9 minutes ago, JohnMo said:

Do you need your heating on when it's 16 degs outside? That's when the heat pump struggles to get rid of the heat.

not mine, but an example of one left to do it's thing

[Beelbeebub]

I redrew the common capacity vs demand graph using the figures for the 5kw york and a made up house thay uses 6kw at -5 and 0 from 12C.

 

 

as you can see there is a significant "zone" below about 5C where the demand is less than the minimum, and we are likely to spend more time between 5 and 12C than below 5C.

 

What is the issue with cycling? I know it is bad, but why?  Is it wear on the pump? is it efficiency? How does the short cycling affect efficiency?

[JamesPa]

25 minutes ago, Beelbeebub said:

I redrew the common capacity vs demand graph using the figures for the 5kw york and a made up house thay uses 6kw at -5 and 0 from 12C.

 

 

as you can see there is a significant "zone" below about 5C where the demand is less than the minimum, and we are likely to spend more time between 5 and 12C than below 5C.

 

What is the issue with cycling? I know it is bad, but why?  Is it wear on the pump? is it efficiency? How does the short cycling affect efficiency?

Start up losses, wear, and it means you are running at a higher ft than is really needed.

[DanDee]

37 minutes ago, Beelbeebub said:

I redrew the common capacity vs demand graph using the figures for the 5kw york and a made up house thay uses 6kw at -5 and 0 from 12C.

 

 

as you can see there is a significant "zone" below about 5C where the demand is less than the minimum, and we are likely to spend more time between 5 and 12C than below 5C.

 

What is the issue with cycling? I know it is bad, but why?  Is it wear on the pump? is it efficiency? How does the short cycling affect efficiency?

The issue with the hp cycling uncontrolled is to many unnecessary start stops(wear). Depending on the HP it can have an effect on efficiency or not.

I cannot tell you exactly what and how, but some HP's are running efficiently only after the initial 5-10 minutes, other from the start. Some are unable to modulate efficiently such that every start soon triggers a stop and then a restart (forever).

Such my conclusion that is better to control this with a fixed low temp and a thermostat. to keep it simple, let it run at 35 flow unless bellow 0C outside(random numbers)

 

good COP but too many starts on panasonic

 

 

Mitsu 6kW good COP on UFH without DHW, but is never able to modulate down to 3kW just goes berserk triggering start stops but very good output when needed

 

 

 

Mitsu 14kW left on it's own, it's either cycling it's brain out or not, random.

 

 

 

 

Edited July 29, 2023 by DanDee

[Beelbeebub]

29 minutes ago, JamesPa said:

Start up losses, wear, and it means you are running at a higher ft than is really needed.

I'd be interested in the "wear" bit. I wonder what mechanism is causing the accelerated wear? The only one I can think of is lubricant starvation at startup, but that shouldn't be an issue if the thing only shut down recently.

 

WRT efficiency, I can imagine there are some losses related to ramping up to operating minimum speed and the time taken to build pressure.  But ultimately the issue is "is the (S)COP better than 3.5¹?. Is chasing the last few % of efficency worth pushing up the cost with large buffers and complex setup Vs just fitting a box outside.

 

Gas boilers cycle quite a bit in shoulder months. Theoretically it increases wear (thermal cycling) and reduces efficency but nobody cares because slapping a box on the wall is much cheaper and simpler than lots of complex calculations, a box on the wall and a load of gubbins.

 

The HP above (Panasonic) seems to be cycling like mad and still hitting well over 4 on the COP. At that point, I'd say it's fine.

 

¹ Or whatever the financial break even point is 

Edited July 29, 2023 by Beelbeebub

[JamesPa]

47 minutes ago, Beelbeebub said:

But ultimately the issue is "is the (S)COP better than 3.5¹?. Is chasing the last few % of efficency worth pushing up the cost with large buffers and complex setup Vs just fitting a box outside.

My conclusion is this:  If it's sized correctly and has a decent modulation then no.  If it's well oversized then the installer will put in a badly set up buffer costing even more to run.

 

Some of the more innovative installers have clearly come to the same conclusion.

 

Edited July 29, 2023 by JamesPa

[Beelbeebub]

27 minutes ago, JamesPa said:

My conclusion is this:  If it's sized correctly and has a decent modulation then no.  If it's well oversized then the installer will put in a badly set up buffer costing even more to run.

 

Some of the more innovative installers have clearly come to the same conclusion.

 

What's interesting is the range I looked at had the same lower bound for the 5, 7 and 9 kw units.  Your oversize issues will be no worse if you had a 5 or 9kw unit.  The step up to the next size (12-16kw) does step the lower limit up.

 

I wonder how many problem installs are related to oversize Vs undersize?.

 

 

 

 

[Beelbeebub]

Looking at the stats, most UK homes have a max heat requirement under 10kw.

 

If you had a simple outdoor unit (heatpump and PHX) rated to a max of say 3kw at -7. That would likely have a lower band around the 1.5kw at 15C.

 

If the unit was cheap (say well under £1k) and (crucially) pretty small (say 500x500x300) you could fit multiple units for 3, 6, 9, 12 kw max.  You could modulate down by just running on unit.

 

The key bit would be a small and cheap single unit, not much more than the cheap pool heaters.

[JohnMo]

Why do you need multiple units just stop people splitting their heating system into a zone for each room. Just have enough water engaged all the time then no issue.

[JamesPa]

9 minutes ago, JohnMo said:

Why do you need multiple units just stop people splitting their heating system into a zone for each room. Just have enough water engaged all the time then no issue.

And size it correctly in the first place.  Of course it does help if manufacturers make products which are bomb proof, but at some point the installation industry needs to take some responsibility.

Edited July 29, 2023 by JamesPa

[Beelbeebub]

23 minutes ago, JohnMo said:

Why do you need multiple units just stop people splitting their heating system into a zone for each room. Just have enough water engaged all the time then no issue.

It's.twofold.

 

For when the whole house demand in late spring is far below the modulation of the HP sized for whole house demand in deep winter

 

And to make the logistics, installation and price low. Just slap 2 or 3, or even 4 if it's a big place, units on the outside. So extreme economies of scale.

 

If a unit fails, no probs, can be replaced quickly (no waiting for the right size unit) and unless you are a small flat with 1 unit, you still have the other units providing heating and DHW while you wait.

 

Just a thought experiment. What we need is a unit than can modulate down low enough, reliably, to run without needing a buffer or similar.

[JohnMo]

18 minutes ago, Beelbeebub said:

Just slap 2 or 3, or even 4 if it's a big place,

I have 2 acres, and getting one small unit in a place I and wife was happy with was not easy, can't imagine anyone agreeing to 4 units.

[Beelbeebub]

55 minutes ago, JohnMo said:

I have 2 acres, and getting one small unit in a place I and wife was happy with was not easy, can't imagine anyone agreeing to 4 units.

4 *small* units.

[sharpener]

On 29/07/2023 at 14:35, Beelbeebub said:

4 *small* units.

 

The first unit may be PD*, but after that they all need express Planning Permission.

 

*principal requirements are MCS install and not more than 0.6 cu m, which is likely to apply to small units.

 

 

On 29/07/2023 at 12:20, Beelbeebub said:

What's interesting is the range I looked at had the same lower bound for the 5, 7 and 9 kw units.  Your oversize issues will be no worse if you had a 5 or 9kw unit.  The step up to the next size (12-16kw) does step the lower limit up.

 

If the mfr varies the refrigerant charge I would expect the min would vary along with the max. If they just limit the max by a software truncation then it wouldn't, seems like York are in the second category. So are Vaillant, the 10 and 12 kW uinits both have 1.3 kg R290 and AFAICS the output map for the 10 is simply a subset of the 12's with the top end chopped off.

 

[Beelbeebub]

7 hours ago, sharpener said:

The first unit may be PD*, but after that they all need express Planning Permission.

 

*principal requirements are MCS install and not more than 0.6 cu m, which is likely to apply to small units.

The idea (such as it is).would be the units could.be fixed together so they are one unit. Say 2x1.or 2x2 or 1x2 or 3x1 or whatever.

 

Again, this points to the need for some regulatory changes to boost HP take-up.

[SteamyTea]

41 minutes ago, Beelbeebub said:

The idea (such as it is).would be the units could.be fixed together so they are one unit. Say 2x1.or 2x2 or 1x2 or 3x1 or whatever.

I have often thought that modular design would be a good idea with heat pumps.

[JamesPa]

46 minutes ago, SteamyTea said:

I have often thought that modular design would be a good idea with heat pumps

I think you could get away with 6kW units.  That's about the minimum you would want for dhw and they would modulate down to say 2kW below which a 10pc hit on electricity consumption won't matter much.

 

But I suspect the volumes easily justify making a variety of units.   The UK requirement alone is 1.4m (that's the number of gas boilers replaced each year).  So I'm not sure the modular concept is actually essential.

[SteamyTea]

25 minutes ago, JamesPa said:

So I'm not sure the modular concept is actually essential.

Not essential, but could get installers out of a hole.

 

This idea of limiting a heat pump via software is what Tesla (and other car makers) do.

Reminds me of the Top Gear rant about cheese and Ferrari.

 

 

[JamesPa]

23 minutes ago, SteamyTea said:

Not essential, but could get installers out of a hole.

 

This idea of limiting a heat pump via software is what Tesla (and other car makers) do.

Reminds me of the Top Gear rant about cheese and Ferrari.

 

 

Fair enough.  Daikin are same, all pumps in any given range identical except for max op.  Mitsubishi 8.5 and 11.2kW models are different tho.

 

Installer should be allowed to update if it's software controlled, but of course the min, which is critical doesn't change.