ASHP set up

[Pete]

I have finally come to the conclusion that we are going to fit an ASHP and cylinder to our property. Over the years we have been drawn to the Sunamp, Sunamp and Willis heater courtesy of @TerryE but with the recent problems encountered and the uncertainty of how the system works if/when you have a problem does not appeal to us (Apologise to all those Sunamp owners out there).

So having chosen ASHP it brings with it the problem of designing/installing the system and even though I have plumbed houses and fitted central heating systems the thought of this seems quite daunting.I have never fitted a cylinder before so this in itself is new territory so I am appealing to people who have done this themselves @joe90 , @ProDavefor any guidance you can pass on to me and may be some more help from @Nickfromwales and @PeterWif you can spare the time. I am struggling to get anybody locally who can just fit this low KW ASHP with cylinder without wanting to double the capacity, have it interact with the space station for telemetry and spend a whole week on fancy control systems. 

I have looked at the plug n play systems from the likes of LG and Samsung which would be very easy (ish ) to set up but would cost quite a bit more. I know I need an inverter in the ASHP and a blending valve(!) now so you can see I need quite a bit of advice to be able to understand the system and what I require. The house is Passive so will be minimum heating and I intend to keep the DHW temp low like Joe and Dave so I am trying to give you as much info to help with your advice hopefully. I know people have bought their cylinders from Telford but not sure what cylinder to buy? We will be doing solar PV at some point just not sure when. @joe90has mentioned having a buffer tank but he is not sure whether he actually needed it although he has his immersion in this tank I know you can have an immersion in the main cylinder and if I had a Willis heater as an immersion heater this could double up as a stand by if I ever have ASHP problems but how does this all connect together!!

Hope you understand my dilemma and hope you can help me design and understand my DHW and UFH system from the start to the finish!!

[ProDave]

Don't over think it.

 

An ASHP is a source of heat.  Think of it as a system boiler.  That heat connects to either the heating (presumably UFH) or the hot water tank via a couple of motorised valves.  That plumbing is withing the capabilities of any plumber worthy of that title.

 

The electrics can be a little more complicated than a system boiler and are very dependant on what make of ASHP you choose. They are not as standard in that respect as a system boiler.  But again any electrician that can read the manual should be able to connect it.

 

A good option which is well regarded is the Mitsubishi Ecodan ASHP which can be bought with a pre plumbed matching unvented hot water cylinder.  That is probably the most simple system to install.

 

I run my system without a buffer tank without issue but some swear by them.

 

 

[PeterW]

@Pete questions for you..

 

size of house

Insulation levels

Heat loss calcs done ..?

Number of showers / bathrooms

Plant room ..?

UFH / Rads / Towel rails ..?

 

Lets have that lot and then work out what’s needed ..!

 

[Pete]

3 minutes ago, PeterW said:

@Pete questions for you..

 

size of house

Insulation levels

Heat loss calcs done ..?

Number of showers / bathrooms

Plant room ..?

UFH / Rads / Towel rails ..?

 

Lets have that lot and then work out what’s needed ..!

 

Hi @PeterW

Size of house 312 Sq/m

Insulation: Passive slab, walls with full fill 300mm insulation and warm roof with same thickness of insulation (very warm with just me working in there!!)

Heat Loss: 179kJ/K( Hope this what you are after, got this from the SAP Calcs)

3 bathroom with three showers

Yes to Plant Room

Yes to UFH all one zone. No Rads and wired for towel rails but non fitted.

MVHR will be fitted.

Many thanks for your input, much appreciated

[PeterW]

What’s the spacing on the UFH pipes ..? Got the manifold mixer ..?

[Nickfromwales]

Thickness of slab / screed? UFH pipes in which ?

[scottishjohn]

10 hours ago, ProDave said:

A good option which is well regarded is the Mitsubishi Ecodan ASHP which can be bought with a pre plumbed matching unvented hot water cylinder.  That is probably the most simple system to install.

this was my choice for fitting to house - not a new one

I already had UFH but was changing from LPG boiler heat source  and still use part of my old system control --as in zone  valves and timers for each room 

-been very happy with  it 

[Pete]

9 hours ago, PeterW said:

What’s the spacing on the UFH pipes ..? Got the manifold mixer ..?

200mm and already have the manifold Wunda but no blending valve☹️

[Pete]

6 hours ago, Nickfromwales said:

Thickness of slab / screed? UFH pipes in which ?

100mm, part of Passive base

[A_L]

11 hours ago, Pete said:

Heat Loss: 179kJ/K( Hope this what you are after, got this from the SAP Calcs)

 

Technical point,  kJ/K cannot be correct as it has no element of time. A Watt is one Joule per second (J/s) and a specific heat loss of 179W/K is probably meant. This would be about right. Is there a separate value for thermal bridges?

[PeterW]

Lets start at 9KW ASHP and a 400 litre UVC HP spec from Telford, 75 litre buffer tank and also get the blending set for the manifold (just hope it set up to allow the pipe centres to line up...)

 

Personally, I don't like the pre-plumbed cylinders as they are expensive for what they are. There are circa £250 of bits on the tank and they add over £600 to fit them onto the tank. They assume too that it is wired as S-Plan, which may not be ideal in all instances. With a heat pump setup you are better off using a diverter valve rather than zone valves as there is always an open circuit so you don't get over pressure issues with closed valves.

 

Heat load for the heating will be low, hence the need for the buffer tank as the ASHP will short cycle otherwise.

[scottishjohn]

4 hours ago, PeterW said:

Lets start at 9KW ASHP and a 400 litre UVC HP spec from Telford, 75 litre buffer tank and also get the blending set for the manifold (just hope it set up to allow the pipe centres to line up...)

 

Personally, I don't like the pre-plumbed cylinders as they are expensive for what they are. There are circa £250 of bits on the tank and they add over £600 to fit them onto the tank. They assume too that it is wired as S-Plan, which may not be ideal in all instances. With a heat pump setup you are better off using a diverter valve rather than zone valves as there is always an open circuit so you don't get over pressure issues with closed valves.

 

Heat load for the heating will be low, hence the need for the buffer tank as the ASHP will short cycle otherwise.

 

you personal opinion is noted

certainly not the case with my system -each zone has its own  7 day programmer+thermostat in room

I doubt new house will be as complicated with MVHR and gaps under doors etc -zones will be much simpler 

-so heat source is only turned on and pumps only run when that zone calls for heat which activates both pump+heat source 

as for being an expensive option --not as expensive as you suggest considering the high spec and efiecent plate heat exchange +2 bronze pumps +all control circuitry+high class plumbing +filters+expansion vessel +pressure gauge  which it comes complete with

all you have to supply is one electric supply +one cold feed then just connect to your DHW+heating circuit 

and i doubt any plumber /electrician would ever get all the bits in as  compact a unit and so  that you can get at everything for service

plus if  you have problems then  same man to repair all the ASHP system + its associated bits

all you have is a simple wifi or hard wired panel  for you to control everything about it

 

new house when built I will be looking at same thing again and comparing with other units on the market at that time -that has a proper service network backup -I will not be wanting to guddle about with heating systems in my 80,s

 cheap basic ASHP + cheapest tank and pumps etc etc will not be on my list 

this is my personal view on the subject 

 "the quality is remembered long after the price is forgotten"

Edited July 21, 2020 by scottishjohn

[joe90]

Well I have a 4 kW ASHP feeding a buffer tank which feeds UFH via blending manifold set to 25’ In the heating season the buffer is permanently heated and when the single room stat in the hallway calls for heat the pump on the manifold is activated. I only have one zone, the whole downstairs. I was recommended a buffer tank to stop short cycling but others here don’t have them with no problem. The buffer tank also has an immersion to give me backup heating if the ASHP is offline for servicing/breakdown, but a Willis heater would provide this backup if I had no buffer. Two reasons fir having the buffer, less inhibitor/antifreeze, and instant access to heat for the UFH rather than waiting fir the ASHP to get up to temp. Buffer tank temp is controlled by tank stat set at 40’. The ASHP set to provide water at 48’ for any use. I have never seen the ASHP defrost.
 

DHW, when the Telford DHW tank calls for heat a signal activates a diverter valve fir the manifold ASHP to heat DHW. 

 

I am a Luddite and like simple uncomplicated tech free solutions (less to go wrong IMO) and find my setup works very well.

[PeterW]

14 minutes ago, scottishjohn said:

as for being an expensive option --not as expensive as you suggest considering the high spec and efiecent plate heat exchange +2 bronze pumps +all control circuitry+high class plumbing +filters+expansion vessel +pressure gauge  which it comes complete with

 

OK so this one is even worse - a normal UVC does not need a PHE, and there is DHW external mixing where a 3.3kw internal coil needs no moving parts. It essentially adds another pump and another system to go wrong, with 3 pumps where one would do assuming you cannot remove the circulation pump for the heating system. And at over £2000 for the cylinder that is eye watering..! This can be massively simplified and not require anything close to the components.

 

I have installed a single circuit ASHP that has one diverter valve, one pump and one zone valve. It is run from a standard dual channel controller that is wired in "W Plan" which any plumber could work on as the heat pump needs a single NV switch to trigger the heat pump. That provides all the heat and DHW to a 300 litre UVC and 85sqm UFH setup and it took less than  2 days to install and wire. It cannot get much simpler than this.

 

 

 

 

[ProDave]

I have mine on individual 2 port valves but I wish I had know about a 2 position diverter valve. The only 3 port valves I knew about at the time were the mid position ones.

[joe90]

3 hours ago, ProDave said:

but I wish I had know about a 2 position diverter valve. The only 3 port valves I knew about at the time were the mid position ones.

I found that out the hard way, it’s still in my workshop somewhere .!

[Pete]

8 hours ago, PeterW said:

Lets start at 9KW ASHP and a 400 litre UVC HP spec from Telford, 75 litre buffer tank and also get the blending set for the manifold (just hope it set up to allow the pipe centres to line up...)

 

Personally, I don't like the pre-plumbed cylinders as they are expensive for what they are. There are circa £250 of bits on the tank and they add over £600 to fit them onto the tank. They assume too that it is wired as S-Plan, which may not be ideal in all instances. With a heat pump setup you are better off using a diverter valve rather than zone valves as there is always an open circuit so you don't get over pressure issues with closed valves.

 

Heat load for the heating will be low, hence the need for the buffer tank as the ASHP will short cycle otherwise.

Hi @PeterW, thanks for your valued input. Why 9kw ASHP as you say the heating load will be low? (I am not doubting your ability but just trying to understand the reasoning behind your judgement).

What is S plan, W plan etc?

Do Telford just do cylinders?

Any chance you could do a drawing for the pipe layout and wiring diagram if that is not to much to ask so I can get my head round d it all.

Many thanks

[joe90]

@Pete here is the docs regarding my ASHP, only difference is UFH rather than radiators, plumbing and electrical diagrams included may give you some insight.

https://forum.buildhub.org.uk/applications/core/interface/file/attachment.php?id=8556

[Pete]

Thanks John, have you highlighted the relevant pages?

[Pete]

2 hours ago, Pete said:

Hi @PeterW, thanks for your valued input. Why 9kw ASHP as you say the heating load will be low? (I am not doubting your ability but just trying to understand the reasoning behind your judgement).

What is S plan, W plan etc?

Do Telford just do cylinders?

Any chance you could do a drawing for the pipe layout and wiring diagram if that is not to much to ask so I can get my head round d it all.

Many thanks

Understand S plan etc now and found Telford so know they only do cylinders

[joe90]

Yes mine is a W plan (in that it uses a 3 port motorised valve without a mid position) but despite documentation saying hot water is the default (3 way valve not energised) I found, after it would not work properly, that the ASHP sends its power to the valve to supply hot water, so the default was in fact heating (UFH). Simple remedy of turning the valve round.

[PeterW]

9Kw will heat a 400 litre UVC to 47c in a couple of hours at E7 rates, boost it to 65c for 90 mins in the last bit of the E7 period and you’ve got all your hot water for a day for pennies. 
 

ASHP kicks in at say 4am, warms the slab so the house is toasty through the day. Boost in the late afternoon if needed. 
 

A 9Kw will also not be stressed at that sort of load - could probably drop to a 5Kw but the price difference is buttons. 

[Pete]

On 21/07/2020 at 11:27, PeterW said:

Lets start at 9KW ASHP and a 400 litre UVC HP spec from Telford, 75 litre buffer tank and also get the blending set for the manifold (just hope it set up to allow the pipe centres to line up...)

 

Personally, I don't like the pre-plumbed cylinders as they are expensive for what they are. There are circa £250 of bits on the tank and they add over £600 to fit them onto the tank. They assume too that it is wired as S-Plan, which may not be ideal in all instances. With a heat pump setup you are better off using a diverter valve rather than zone valves as there is always an open circuit so you don't get over pressure issues with closed valves.

 

Heat load for the heating will be low, hence the need for the buffer tank as the ASHP will short cycle otherwise.

With regards to the buffer tank and preventing short cycling, my UFH pipes are 5 zones but no zone valves so really one large zone. The house is mainly all ground floor so there is a large amount of water already in the pipes (house area 8m x 25m for the pipe area on 200mm centres, PH) so I would think I would be ok to omit the buffer tank as others have stated they have not fitted a buffer tank and their system works ok? TIA

[PeterW]

Zone valves aren’t your problem - it’s the mixer valve. As the water warms in the pipes it needs less “hot” water from the ASHP so the blending valve starts to close. Without either a low loss header or a buffer, the blending valve will restrict the flow, potentially causing you flow issues on the ASHP. 

[Pete]

1 hour ago, PeterW said:

Zone valves aren’t your problem - it’s the mixer valve. As the water warms in the pipes it needs less “hot” water from the ASHP so the blending valve starts to close. Without either a low loss header or a buffer, the blending valve will restrict the flow, potentially causing you flow issues on the ASHP. 

Just dug my UFH box out and I think I may have a mixing/blending valve after all?

The temp range on it is 30 to 70, will this be ok for my PH build? TIA