Vaillant ashp (my battle with).

[ProDave]

4 minutes ago, zoothorn said:

why is there 105 litres of water discrepency, between a system that has a heater, to one that hasn't?

In cold weather, the outside unit of an ASHP can ice up.  When this happens it needs to be defrosted.

 

To do this, the system reverses for a short time and actually removes heat from the water in the system in the house to warm up and defrost the outside unit.

 

It requires a certain amount of water in the heating system to do this, otherwise it would cool that water down too much during defrost.

 

Some ASHP's have a backup electric heating element.  Those that do, can turn that on while it is defrosting, so some of the heat to defrost comes from that and less from the water in the heating pipes, so less water volume is needed.

[AliG]

Just what @ProDave said.

 

You don't really need to know the ins and outs of it. You can either have a backup heater and no buffer as you do at the moment or a buffer and no backup heater as currently proposed by the installer.

 

You just need to ask them why the new ASHP does not have a backup heater and no buffer like the current one.

[ProDave]

Gentlemen, speaking with my moderaters hat on, some posters are starting to directly insult others.  Those posts have been removed.  Please play nicely.

[zoothorn]

5 minutes ago, ProDave said:

In cold weather, the outside unit of an ASHP can ice up.  When this happens it needs to be defrosted.

 

To do this, the system reverses for a short time and actually removes heat from the water in the system in the house to warm up and defrost the outside unit.

 

 

THIS much, ProDave, I do know... because it is the very source of my woes/ my battle with Vaillant/ because the unit that houses the pump to drive the water around during this satanic 11pm-7.30am frost cycle... was placed.. 1.5m away from a bed, & which was so loud & contiuous, it disturbed sleep in the adjacent bedroom & heard clearly in every corner of the house.
 

THIS is the same cycle, which luckily with your different mfr unit, you are nothing whatsoever similarly disturbed by. Because. Yours isn't faulty. Mine is/ was.

 

Zh

[zoothorn]

15 minutes ago, ProDave said:

It requires a certain amount of water in the heating system to do this, otherwise it would cool that water down too much during defrost.

 

Some ASHP's have a backup electric heating element.  Those that do, can turn that on while it is defrosting, so some of the heat to defrost comes from that and less from the water in the heating pipes, so less water volume is needed.

I'll need a day to comprehend just these last two paragraphs. They just read double-dutch to me. Read these 3x now, yet still cannot understand the relationship between an additional heater & a tank.
 

I judt don't think Im going to get it ProDave, even if you used stop motion stuffed animals, lego buffer whatnots, & fully slowed it down for the fully retarded.

 

Thanks, Zoot

[PeterW]

Just to put a quick correction to this - the Arotherm 10kW split is actually an f-gas split so the backup heater is there to maintain heat in the water system to allow the gas reversal - there is no water in the outside unit …

If they are fitting an Arotherm Plus 10kW then I’d be surprised if they aren’t just fitting the 40 litre wall mounted decoupler - it’s the same as the hydro unit inside today broadly on size, but doesn’t have all the heat exchanger for gas to water, and it doesn’t have the backup heater inside it. The backup heater is a 6kw separate unit but I do wonder if the reason this is not being specced is down to power issues or the need to run new cabling for it.

 

nice thing on the new Arotherm plus is the flow temps will be 55°C or so which means warm rads ..!

 

[HughF]

Attached, the Saturn air sales ‘heat pumps’ guide, which does quite a good job of explaining the concepts that have been discussed at length in this thread. Those being, defrost cycle & ‘how to use’…

 

 

download.pdf

[Gone West]

11 hours ago, zoothorn said:

Hi GW. Well this is one angle I hadn't thought of. Great. That being asking the if I can pay, for an entirely different mfr buffer, of the same size they insist.. & go shopping for a slimmer one. And go around here evaluating where the heck this could go. At least if slimmer, I can possibly find one spot without ruining my cottage. Cant be the cupboard as its likely not tall enough.

 

But they'll counter this saying they cannot fit other mfr's equipment, or your guarantee is shot doing so, or simply their fitter says no.

I would be surprised if Vaillant didn't make different shaped buffers as it's going to be a common problem in many houses.

[DanDee]

59 minutes ago, Gone West said:

I would be surprised if Vaillant didn't make different shaped buffers as it's going to be a common problem in many houses.

to an extent

[zoothorn]

@PeterW is the ARotherm plus 10kw, a 'monoblock'?

 

I couldn't quite understand the significance of your mentioning water outside bit.. but my eyes lit up with the higher flow temp.

 

Maybe, just maybe they chose this partly because I had mentioned even in my new build rooms, it was impossible to get them warm, using my current 'split' system, unless I ramped up the flow temp (+ some other upping of a level to max) which THEY themselves told me how to do as a niggle I had -paling into insignificance vs my overnight cupboard noise- which was a frustration at the ashp rad performance.

 

This performance niggle, I hear on phone moan-ins even on radio4. So many people think as I do, their performance is nigh on hopeless. UNLESS of course, you have a super-scandi-built-home (my term) to contain the paltry heat emitted. Most UK homes don't fit this category, so this whole ashp venture/ shift IMHO, is so poorly thought out, & also hoodwinking UK customers (even ones grateful to get one via a grant, despite a protracted intrusive noise "battle" with a mfr..) that they're a good idea for their home. The cost now to run them too, apparently, is huge too: 50% of the moan-in calls I hear on R4 are this.

 

Thanks. I'll email my nice woman @Vaillant whose reinstated the offer to me (we agree we're both stuck at this buffer 'hurdle' is the situation) if the monoblock is this one you refer to.

 

Thanks, Zoot

[zoothorn]

1 minute ago, DanDee said:

to an extent

Bravo. Thanks alot for this pinpoint post. I'll even email this example to my nice woman @ Vaillant.

 

Zh

[JohnMo]

10 minutes ago, zoothorn said:

Bravo. Thanks alot for this pinpoint post. I'll even email this example to my nice woman @ Vaillant.

 

Zh

I wouldn't get to excited - that's a cold water storage cylinder, for rainwater etc. Not a buffer being discussed here, very different things.

[dpmiller]

"500 litre baffled water tank"

 

eh?

[zoothorn]

2 hours ago, HughF said:

Attached, the Saturn air sales ‘heat pumps’ guide, which does quite a good job of explaining the concepts that have been discussed at length in this thread. Those being, defrost cycle & ‘how to use’…

 

 

download.pdf 417.21 kB · 2 downloads

Hi Hugh. Hugely grateful for this.

 

Even on page 2, with the diagram, my head still aches trying to understand the basics though (eg it suggests indoors, a fan moves the compressed [water or air?] around.. & my head hits a brick wall). A fridge, in my world & most people's too, isn't some super-simple device like an oven is fir example. It's next-level design.
 

Personally I think it needs a prior-level explanation, for people who haven't studied engineering frankly: likely 95% of customers. 

 

Nevertheless I might be able to brave the buffer/ extra heat sutuation page. But I don't expect to understand that either.

 

 

[HughF]

6 minutes ago, zoothorn said:

Hi Hugh. Hugely grateful for this.

 

Even on page 2, with the diagram, my head still aches trying to understand the basics though (eg it suggests indoors, a fan moves the compressed [water or air?] around.. & my head hits a brick wall). A fridge, in my world & most people's too, isn't some super-simple device like an oven is fir example. It's next-level design.
 

Personally I think it needs a prior-level explanation, for people who haven't studied engineering frankly: likely 95% of customers. 

 

Nevertheless I might be able to brave the buffer/ extra heat sutuation page. But I don't expect to understand that either.

 

 

If you took the door off your fridge, and then glued the fridge through a fridge shaped hole in the wall of your house, with the back of the fridge inside, you’d be cooling the world, and pumping/dumping the heat into your house. The heat comes from the fact that it has been removed from the inside of the fridge, which, because you’ve ripped the door off, continues to get warmed by the environment.

 

Imagine if you poured water over the back of the fridge, scooped it up, and then pumped it through radiators. This is how your heat pump works.

 

You could just as easily forgo the water and just point a fan at the back of the fridge - you’ve now made an air-air heat pump and you don’t need any radiators.

 

This is precisely the level of explanation that Graham Hendra goes into in his first book. You should grab a copy from Amazon.

Edited September 2, 2023 by HughF

[Beelbeebub]

Don't bother trying to understand Heatpumps if you are struggling with those explanations. 

 

It's a black box of stuff that you put electricity in and hot water comes out. That's all you need to know. 

 

If there is insufficient volume of water in the radiators and pipes or your plumbing system is laid out in a certain way, then you need a "buffer vessel" of a certain size. 

 

This buffer vessel can be smaller if you also have something called a "backup heater". 

 

As you have struggled with the explanations provided i'd suggest you leave it to your installer whose job it is to install HP systems. 

[DanDee]

1 hour ago, JohnMo said:

I wouldn't get to excited - that's a cold water storage cylinder, for rainwater etc. Not a buffer being discussed here, very different things.

 

1 hour ago, dpmiller said:

"500 litre baffled water tank"

 

eh?

 

 

As an alternative size/shape, not as a direct replacement. The problem is that buffers universally are never that shape, to work in constrained situations.

2 hours ago, Gone West said:

I would be surprised if Vaillant didn't make different shaped buffers as it's going to be a common problem in many houses.

 

 

 

 

 

 

Edited September 2, 2023 by DanDee

[Beelbeebub]

14 minutes ago, DanDee said:

 

 

 

As an alternative size/shape, not as a direct replacement. The problem is that buffers universally are never that shape, to work in constrained situations.

 

 

 

 

 

 

Buffers need to be pressurised so cylindrical is the norm, though some do have rectangular external casings. 

[DanDee]

12 minutes ago, Beelbeebub said:

Buffers need to be pressurised so cylindrical is the norm, though some do have rectangular external casings. 

That's mostly DHW cylinder rather than buffers.

 

 

Of course buffers universally have the same characteristics,  but for specific situations it doesn't stop(legislation maybe) you from designing something that fits your needs. Low pressure, low temp, any shape-size buffer, with only in/out connections. Basically a water storage tank.

 

 

[DanDee]

@zoothorn you need this

 

[DanDee]

Ultimately a thin but room tall buffer can still be boxed in any corner to solve some of the issues, so the sky is limit.

[Beelbeebub]

25 minutes ago, DanDee said:

Of course buffers universally have the same characteristics,  but for specific situations it doesn't stop(legislation maybe) you from designing something that fits your needs. Low pressure, low temp, any shape-size buffer, with only in/out connections. Basically a water storage tank.

The constraint is physics and economics. 

 

The buffer is necessarily at the same pressure as the rest of the heating system. This is 1bar minimum. 

 

The most efficient shape to withstand internal pressure is a cylinder (ignoring a sphere).

 

If you made a rectangular pressure vessel the walls would need to be a lot thicker and thus heavier and more expensive. 

[AliG]

I think this is getting a bit hypothetical.

 

Ultimately if a buffer of circa 100litres is needed then it will take up a minimum amount of space.

 

I spent a bit of time looking and found one square buffer here -

https://www.advanceappliances.co.uk/product/141-buffer-stores/

 

However it is short and squat so wouldn’t particularly help unless there is a place where it would fit.

 

I don’t believe anyone makes a very tall skinny buffer. If someone finds one please post a link.

 

I would simply ask the installer/nice lady at Vaillant -

 

1. Can we have a backup heater instead of a buffer?

2. If we have to have a buffer can we have one that fits in the cupboard where the hydraulic unit is or any other space that would work for @zoothorn accepting that there might be a minimum size required.

 

No one needs to know how ASHPs work, why buffers are needed, is this different to other makes of ASHP or anything else.

 

@zoothorn can you just put those two questions to the nice woman at Vaillant and the installer. Just email them if possible and await the response. If the response makes no sense to you then post it here and we can see if we can help.

 

[JohnMo]

First sensible and clear answer - well done. 

[Beelbeebub]

18 minutes ago, AliG said:

I think this is getting a bit hypothetical.

 

Ultimately if a buffer of circa 100litres is needed then it will take up a minimum amount of space.

 

I spent a bit of time looking and found one square buffer here -

https://www.advanceappliances.co.uk/product/141-buffer-stores/

 

However it is short and squat so wouldn’t particularly help unless there is a place where it would fit.

 

I don’t believe anyone makes a very tall skinny buffer. If someone finds one please post a link.

 

I would simply ask the installer/nice lady at Vaillant -

 

1. Can we have a backup heater instead of a buffer?

2. If we have to have a buffer can we have one that fits in the cupboard where the hydraulic unit is or any other space that would work for @zoothorn accepting that there might be a minimum size required.

 

No one needs to know how ASHPs work, why buffers are needed, is this different to other makes of ASHP or anything else.

 

@zoothorn can you just put those two questions to the nice woman at Vaillant and the installer. Just email them if possible and await the response. If the response makes no sense to you then post it here and we can see if we can help.

 

That looks like a very good solution to ZTs problem. 

 

It must be rectangular in section internally to get 100l. So they must have some fairly hefty walls, but that also. Means stuff can sit on top. 

 

(I've fitted 2 of their thermal stores and they seem well made) 

 

It looks like it would fit in their cupboard and still provide ample space above for storage.

 

If ZT's installers are happy then it's problem solved.