Non-domestic ASHP installation ( light commercial )

[Nickfromwales]

Im currently spec'ing an old school conversion ( single storey existing building to 5 holiday rental units plus one domestic residence, same building ) and am facing the heating / water 'split' dilemma. Need the domestic side and non-domestic side split into separate systems so the RHI payments can be applied accordingly ( if they choose to go that route ). I need ( equal to or lesser than ) 32Kw total of space heating plus 2 separate DHW systems.

Thinking of pairing 2 x 15kw HP's for the 5 rentals, ( redundancy for maintenance or one unit failing etc ), feeding into one large buffer tank via a 'common rail' arrangement ( so an unified body of water ) and the two ( rental units ) Ufh manifolds fed off the buffer, with a 180tr UVC with a hot return circuit so instant hot water at all basins. A third 12kw unit then for the domestic dwelling doing Ufh ( via it's own manifold and buffer ) and a 210ltr UVC, ( bath, stand alone shower, basin and loo in the domestic bathroom ). 
The dilemma is whether or not to ask the ASHP's to ramp up to 55oC for DHW production, or to just leave the immersions provide dhw start to finish. These will never go cold so the upper range will only need to be maintained ( eg top up against use or losses ). I've allowed for buffers at the moment so that the each of the Ufh manifolds has a heat battery so that the space heating will continue to be serviced whilst the ASHP's drop out to do DHW, should that be the way to go. 
The cons seems to be just components and complexity of pipework and controls etc ( if doing the split heating and DHW design ), with the pros being DHW will be produced quicker.

Each of the renters will have a tank-fed electric shower, no bath, and just a basin for hand wash, plus one communal cloakroom WC so very little DHW required for these units. 

 

Anyone have any thoughts on the potential revenue that would be generated by the RHI, vs doing a cheaper non-MCS install. 20 years of lower rate plus 7 years domestic is on the table. Going non-MCS will probably save over £5k. Waiting for a positive response from the customer before I progress to the maths stage, but thought I'd float it here first, for some extra reading material if nowt else .

[Stones]

Bigger UVC for the domestic side so you could set the ASHP to provide DHW in the 47 - 50C range?  

 

From all I hear about the hoops other people are having to jump through to claim RHI, I think its best avoided.

 

 

[SteamyTea]

The rates are here:

http://www.icax.co.uk/Renewable_Heat_Incentive_tariff_tables.html

 

Have you looked into becoming your own RHI/MCS installer.  The company I worked for fitted a PV system to the bosses house to get accreditation.  Was not that costly, and I seem to remember that the cost for an RHI cert was not too much (arond 700 quid).  It was 5 years ago, so things may have changed.

[Nickfromwales]

On 14 August 2016 at 11:03, Stones said:

Bigger UVC for the domestic side so you could set the ASHP to provide DHW in the 47 - 50C range?  

 

From all I hear about the hoops other people are having to jump through to claim RHI, I think its best avoided.

 

 

I've left the information with the customer for them to ascertain the ( possible ) benefits, but I steered them off LPG for the moment. They're already going to be massively better off in a 10 year period going for ASHP's, as the building they're currently in, ( of similar size but not as well insulated etc ) has a yearly bill of nearly £5k for LPG. 

I was estimating that they'll use around £2k of electricity to achieve the same £5k of energy consumption, worse case. They could also install Pv but I doubt they'll go for it tbh, due to the combined capital expenditure. They started pulling faces at my quote of £21k to fit the HP's and supply and first fix all the heating and hot water system, ( less Ufh as it's existing ), which I thought was keen price to say the least . Their estimated cost for the LPG boiler install is around £13k so they only need to save £7-8k fuel costs to break even on the bigger price. Over 10-15 / 20 years the HP's make much better sense but I think they're looking at a 10 year plan, which is a bit short-sighted IMO. 

 

1 hour ago, SteamyTea said:

The rates are here:

http://www.icax.co.uk/Renewable_Heat_Incentive_tariff_tables.html

 

Have you looked into becoming your own RHI/MCS installer.  The company I worked for fitted a PV system to the bosses house to get accreditation.  Was not that costly, and I seem to remember that the cost for an RHI cert was not too much (arond 700 quid).  It was 5 years ago, so things may have changed.

 

Ive thought about it, but there's just not enough of that type of work firing across my bow. I'll prob try and find an MCS fitter and give him a handsome rate to fit and commission and take the hit. This is my first enquiry for a job where I'm promoting the use of a heat pump, but with a huge area of Ufh, reasonable levels of air tightness and above average insulation etc I think that HP's are a no brainer for this job. The majority of used energy is going to be space heating and the Ufh company gave a delta flow of 28oC so pointless being able to massively exceed that with gas units. They've got 3-phase there so that sides comfortably sorted. 

[Trw144]

One thing Nick, I don't think you need the domestic and commercial element split. If you can do it off one heat pump/system, then some of it being commercial makes it all commercial (or non-domestic in rhi speak).

[Nickfromwales]

Cheers. New territory here for me so all and any input appreciated. 

I was going to fit two large HP 's for the ND side so they could mothball that side of it if it wasn't rented for a few months of the year and also so they had redundancy for reliability / maintenance ( eg one will give some heat whilst other is being serviced / other ) plus I wanted them to idle as much as possible to keep the noise down. 

Need ~32kw of space heating + Dhw. Thought this would be far better split over at least two units, but if a pair of 16/18kw units would suffice, please let me know. Guys due to come back to me at the end of the first week of sept.