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ASHP questions about install and costs of 'bits'


Roz

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Trying to figure out how to go about this ASHP thing, whether to get one company in to supply fit and commission, or buy separately and get electrician and plumber to fit then perhaps an MSC commisson and sign off (have been told that was possible if I pay them £700... but that was a while ago). So I have a couple of questions...

 

- ASHP will power underfloor heating and an UVC. Does the heating need to come out of the UVC or can the heat pump divert to two sources - the underfloor heating and the UVC. So then the heating isnt drawing out of what will be a small tank that we want to reserve for DHW.

 

- For those that have bought their heat pump and cylinder separately, how much was extra 'stuff' needed to go from these two units, to having them working and feeding into one another? 

 

Thanks in advance!

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The extra "stuff" is just the same as for a normal system boiler.  A couple of motorised valves, a pump perhaps, and if like us you did not want to use the programmer supplied with the ASHP then a conventional boiler programmer.

 

Heat pumps work different to system boilers, they only ever heat DHW or space heating, never both together.  This allows them to run at a different target temperature for heating and a higher temperature for DHW.

 

I run mine direct to the UFH without issue. Some say you should fit a small buffer tank.

 

You need to look carefully at whether it is worth going for an MCS install and claiming the RHI or going for a cheap install and not bothering.  I bought a cheap ebay ASHP and self installed it though that was not without it's problems (the first one they supplied was faulty and I had to kick up a stink to get them to replace it)

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1 hour ago, ProDave said:

The extra "stuff" is just the same as for a normal system boiler.  A couple of motorised valves, a pump perhaps, and if like us you did not want to use the programmer supplied with the ASHP then a conventional boiler programmer.

 

Heat pumps work different to system boilers, they only ever heat DHW or space heating, never both together.  This allows them to run at a different target temperature for heating and a higher temperature for DHW.

 

I run mine direct to the UFH without issue. Some say you should fit a small buffer tank.

 

You need to look carefully at whether it is worth going for an MCS install and claiming the RHI or going for a cheap install and not bothering.  I bought a cheap ebay ASHP and self installed it though that was not without it's problems (the first one they supplied was faulty and I had to kick up a stink to get them to replace it)

Any ballpark costs for the stuff? Also when looking at a ASHP on ebay I realised I would need the control unit for it and its £450 or something, which seems alot - is that what you mean by the programmer?  This was when looking at a samsung gen 6 5kw

 

OK so thats good if I understand you correctly. Because commissioners keep talking to me about how the heat pump will go into the cylinder and the underfloor will then come back out of that, but it doesnt seem to make sense to do that if I don't have to.

 

What is the buffer tank for?

 

My main problem is  just that it all seems a bit beyond my grasp to understand everything I need in order to assess whether I can just buy my own stuff and get plumbers and electricians to install.

 

I'm looking at a company supplying and commissioning a mitsubishi heat pump and pre-plumbed cylinder, supply of is £4400. Commissioning and registering is £900.

PLUS: installation (their 3rd party installation cost was £2000, somewhere in there I presume all required parts and bits are included. We can do our own /outsource our mechanical install though)

 

This is basically too much for us, but is it a false economy to try and do it bit by bit alone.

 

If I was to get a big brand heat pump from ebay I seem to be looking at £1500-1900, plus a Telford Tempest at £800. £2700, inc vat. around £2250 ex vat.

PLUS: installation (I can run pipes and do hep2o but probably installing these is beyond me. so £?) , parts (£? control unit £400??) , perhaps commissioning to get MCS payback (£900)

 

Edited by Roz
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At it's basic level, an ASHP has two pipe connections, flow and return, just like a system boiler.  ANY plumber that can plumb a system boiler can plumb an ASHP

 

The electrics can be a little more complicated, unfortunately every make of ASHP seems to have it's own ideas how it integrates to the rest of the system so unlike aq system boiler it's not just a set of standard wiring, but it is not that difficult you just have to read the manual and understand it.

 

£2000 is way too much to install it.  At a labour rate of typically £200 per day that would be a whole week for both the plumber and the electrician which is ridiculous.

 

And £900 to commission it.  No more than a days work.

 

It's when you get prices like that, that many of us become sceptical  that you are being ripped off with an over inflated cost, with the result the company are creaming off most of the benefit you will get from the RHI payments.

 

And being charged £400 for a controller is madness, that amount of electronics in any other consumer product would be no more than £50  So if seeking an ebay bargain, try and find one that has the controller (if one is needed)

 

No I was talking of adding a boiler programmer as well. I did not have to, but the programmer supplied with mine is a fiendishly complicated thing to understand and use. Yes it would do the job but I doubt anyone in the house would understand it.  So I preferred to just leave that for setting parameters and diagnostics, and use a normal programmer that everyone understands to determine at what times of day it runs heating and hot water.

 

 

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I bought my ASHP on Ebay fir £850, which was a punt but well worth it. I had to source a programmer but frankly not touched since installing it!!!,, (£250). A buffer tank (questionable but does have an immersion in case of ASHP breakdown), i installed it all myself over a couple of days but frankly could have done it in one day and I am not a professional plumber. Electrics were a bit difficult as I designed the set up myself?. A changeover valve and a few odds and sods. I am thinking of installing timers as I might go E7 in the future. Diagrams for what to instal are ready available and a wealth of knowledge here on the forum about the best way to go. 

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2 minutes ago, ProDave said:

At it's basic level, an ASHP has two pipe connections, flow and return, just like a system boiler.  ANY plumber that can plumb a system boiler can plumb an ASHP

 

The electrics can be a little more complicated, unfortunately every make of ASHP seems to have it's own ideas how it integrates to the rest of the system so unlike aq system boiler it's not just a set of standard wiring, but it is not that difficult you just have to read the manual and understand it.

 

£2000 is way too much to install it.  At a labour rate of typically £200 per day that would be a whole week for both the plumber and the electrician which is ridiculous.

 

And £900 to commission it.  No more than a days work.

 

It's when you get prices like that, that many of us become sceptical  that you are being ripped off with an over inflated cost, with the result the company are creaming off most of the benefit you will get from the RHI payments.

 

And being charged £400 for a controller is madness, that amount of electronics in any other consumer product would be no more than £50  So if seeking an ebay bargain, try and find one that has the controller (if one is needed)

 

No I was talking of adding a boiler programmer as well. I did not have to, but the programmer supplied with mine is a fiendishly complicated thing to understand and use. Yes it would do the job but I doubt anyone in the house would understand it.  So I preferred to just leave that for setting parameters and diagnostics, and use a normal programmer that everyone understands to determine at what times of day it runs heating and hot water.

 

 

I get skeptical about it too, but I got some 'ballparks' from other companies for everything and their total came to more than this one including the install price. So I guess theyre all on the high side... Im based in SW by the way. But the company who is looking at commissioning it assumed we would sort our own mechanical install, that was a price I got when I asked for their supply of mechanical install. So I and they always thought we would get that sorted elsewhere, and at that price...we will

 

Yes I was surprised by the commissioning cost, but was told a similar price by another MCS guy (I think he said £650, but I dont know if he would add on building regs registration and MCS registration £150, too, or if its necessary.)

 

I dont think they come with it. I dont know if it is needed because I dont know what they are for I guess! The controller I have found at that price and more at a few places : Monobloc control box Gen 6 MIM-E03CN (shit website sorry) https://www.greenwayenergyltd.co.uk/product-page/samsung-control-panel

I think pre plumbed cylinders have them already (maybe)

 

 

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1 minute ago, joe90 said:

I bought my ASHP on Ebay fir £850, which was a punt but well worth it. I had to source a programmer but frankly not touched since installing it!!!,, (£250). A buffer tank (questionable but does have an immersion in case of ASHP breakdown), i installed it all myself over a couple of days but frankly could have done it in one day and I am not a professional plumber. Electrics were a bit difficult as I designed the set up myself?. A changeover valve and a few odds and sods. I am thinking of installing timers as I might go E7 in the future. Diagrams for what to instal are ready available and a wealth of knowledge here on the forum about the best way to go. 

Thanks Joe, what programmer did you source and what is it for?? 

Timers would be good for us as we are probably going octopus agile. 
How much do you think you spent beyond the ASHP and Tempest?

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Some of the costs quoted for things like installation and commissioning are a bit ludicrous.  As @ProDave says, those prices indicate that there's several times more work than there really is.

 

I bought a 7 kW Glowworm ASHP (really a Carrier unit with a Glowworm badge) that was supplied complete with the controller and delivery for £1,700.  I built a concrete base for it in about an hour, and actually installing it, connecting it to the heating system and wiring it took me a bit over half a day.  I'd never installed one before, but it wasn't at all difficult, the hardest bit was probably deciphering the instructions.

 

The heating and hot water system stuff is pretty much the same as any other system, the only difference being the one that @ProDave has already pointed out, that the unit will switch between heating either hot water or heating, but not both at the same time.  This doesn't really add any more complication though.

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8 minutes ago, Roz said:

Thanks Joe, what programmer did you source and what is it for?? 

Timers would be good for us as we are probably going octopus agile. 
How much do you think you spent beyond the ASHP and Tempest?


the programmer was specific for the (rebadged) Carrier unit (same as @Jeremy Harris). It allows all sorts of peramiters to be changed (heating and cooling curves ?). Once set up I have not changed it, timing with it is frankly too complicated, I’m scared to touch it! So I will use timers instead. As @ProDave says different units have different control units. My list of parts are,

 

buffer tank

change over valve 

expansion tank (two)
DHW tank

pressure reducing valve

immersion heaters (three)

wiring centre

air bleed valve

copper and plastic pipe various.

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19 minutes ago, Roz said:

Timers would be good for us as we are probably going octopus agile. 

 

Wouldn't Octopus Agile be better with something a bit more sophisticated than a timer? Obviously, just keeping out of the evening peak would go a long way but it'd be a bit disappointing to heat your DHW or slab in the night if the wind's going to build up and the price is going to go down the following morning.

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I'm not convinced that Agile makes sense when it comes to trying to run a heating system, TBH.  The heating needs of a house tend to follow the heat loss rate vs inside/outside temperature differential, with a phase lag that is largely determined by the house thermal time constant.  We find that heating overnight on E7 works well, but our heating wouldn't work at all well on Octopus Go (just not enough time to get heat into the slab) and I'm pretty sure it wouldn't work at all well with Agile, either, based on some simplistic modelling I did a while ago, looking at the Agile data provided via this web site: https://www.energy-stats.uk/

 

One thing I found was that, rather unsurprisingly, periods of very cold weather tended to be at times when Agile wasn't offering a very good rate.  For a house that doesn't need a great deal of heating, this can mean that whenever heating is needed the rate is higher than, for example, E7.  This page from that site has the last 18 months of Agile prices: https://www.energy-stats.uk/octopus-agile-south-western-england/  and shows pretty clearly that a fair bit of the time when it's been cold, the Agile tariff has been higher than the 8.148p/kWh we currently pay for E7.

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14 minutes ago, Jeremy Harris said:

I  This page from that site has the last 18 months of Agile prices: https://www.energy-stats.uk/octopus-agile-south-western-england/  and shows pretty clearly that a fair bit of the time when it's been cold, the Agile tariff has been higher than the 8.148p/kWh we currently pay for E7.

That also shows that right now I would be paying about 24p per kWh right now to cook the Sunday roast, which is why I do not want that sort of tariff.

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4 hours ago, joe90 said:

I bought my ASHP on Ebay fir £850, which was a punt but well worth it. I had to source a programmer but frankly not touched since installing it!!!,, (£250). A buffer tank (questionable but does have an immersion in case of ASHP breakdown), i installed it all myself over a couple of days but frankly could have done it in one day and I am not a professional plumber. Electrics were a bit difficult as I designed the set up myself?. A changeover valve and a few odds and sods. I am thinking of installing timers as I might go E7 in the future. Diagrams for what to instal are ready available and a wealth of knowledge here on the forum about the best way to go. 

Following this with interest as we are about to get to the time when to decide how to provide DHW/UFH. 

Current thinking ASHP and cylinder but could do with a imlpe diagram on how people have done it please. (Back of fag packet will do)

Other option to try Willis ( leave some tails to be able to add  ASHP at a later date)and a Sunamp for DHW but need to get cost of Sunamp first. TIA

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I found this diagram but one thing is wrong!,the UFH manifold in the bottom right corner should be fed from the tank, not the pipework from the internal coil. Hope this helps!

FB94E6E6-9EBD-45CB-B4B1-E3785677FDEB.jpeg

Edited by joe90
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11 hours ago, joe90 said:

I found this diagram but one thing is wrong!,the UFH manifold in the bottom right corner should be fed from the tank, not the pipework from the internal coil. Hope this helps!

 

Why? I'm not sure what the point of the coil is in this case, you could just as easily pipe directly into and out of the tank. I suppose it might save on inhibitor, though.

 

More significantly, directly connecting the heat pump to the manifold allows immediate heat to the UFH when the system is starting from cold. Only when the demand from the UFH drops off would you then allow the HP to keep running and heat the tank avoiding short cycling. That way you don't need to keep the tank hot throughout the heating season; particularly in the shoulder months you can allow it to cool off during less chilly spells when there's less need for the UFH.

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15 minutes ago, Ed Davies said:

 

Why? I'm not sure what the point of the coil is in this case, you could just as easily pipe directly into and out of the tank. I suppose it might save on inhibitor, though.

 

More significantly, directly connecting the heat pump to the manifold allows immediate heat to the UFH when the system is starting from cold. Only when the demand from the UFH drops off would you then allow the HP to keep running and heat the tank avoiding short cycling. That way you don't need to keep the tank hot throughout the heating season; particularly in the shoulder months you can allow it to cool off during less chilly spells when there's less need for the UFH.


This was suggested by the welsh wizard, my understanding of this is the buffer tank allows an immersion in case of ASHP breakdown (although a Willis heater is another idea), the buffer with a coil stops the ASHP short cycling, during winter I keep the buffer topped up by ASHP so when the UFH calls for heat a store is immediately available whereas an ASHP will take a while getting up to temp. As my water temp is 48’ for buffer and DHW the tanks are very well insulated and I cannot feel any temp difference in the cupboards that they are in (er indoors mentioned the airing cupboard was not very warm?
 

with hindsight I might not instal a buffer tank if I did this again, there are those here that run their UFH direct from their ASHP with no probs (and I would have a Willis heater as backup).

Edited by joe90
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TBH unless you end up with a very cold snap below -10c for an extended period with the ASHP off then you’ll not really need a very strong solution but at about £5/litre it can soon add on a fair amount if you have to fill all the loops plus a 60 litre buffer at 25%. 

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