LPG BOILER OPTIONS

[Alexphd1]

That's scary quotes or maybe it's me being a tight Scotsman.

Another option. Do you know any good plumbers who would go on a day rate with a exact spec and diagrams to follow, with you providing material?

 

Both ashp's are decent quality but nothing special but personally I prefer a monobloc (quote 1) over a split system due to a simpler system I don't need a refrigeration ticket to commission but not worth the price difference.

Edited August 22, 2017 by Alexphd1

[ProDave]

I have said before, just buy a heat pump and any plumber can install it (okay monoblock only, needs a specialist to gas a split system)  All I have seen from packages systems is big price tags.

 

Do you have any SAP calculations or anything else to actually tell you what your heat input requirements will be? Without that you are guessing what size unit to fit.

[PeterW]

Hitachi quote is barking mad ... that's not a HP spec cylinder either as you need a minimum 3m2 of coil to get the full heat out of that 11kw HP. 

 

Telford UVC is £650 with the toys on it. 

Any ASHP for the £2500 mark will do. 

£1k to install 

Should leave you change from £5k 

 

other than the UVC it's all DIYable too. 

 

There is a Daikin on eBay currently for offers of £2500 too ...

 

[Nickfromwales]

13 hours ago, s2sap said:

(2)  Am I right in saying that the UFH pipes should be 150mm spacing for heat pumps, and gas or oil heating etc should be 200mm spacing? If that is the case can I install 150mm spacing and use it with gas ( in case I change to heat pump later )  - surely the additional cost of the pipe and work wouldn't be THAT much more?

 

(3)  @Nickfromwales You are a fan of Valiant boilers and if I dont want the Vokera boiler the gas company will give me an allowance towards any boiler of my choice - which one would you recommend and roughly what cost would it be? Also how much would a suitable 250L UVC be roughly? I wouldn't need  a buffer tank for the UFH would I?

Fit the pipes at 150mm, as it's your heat demand that'll dictate how many watts per m2 you'll need to get out of your slab . You simply adjust the blending valve temperature on the UFH manifold to suit, starting low and working up daily to what you feel heats quickly enough but is comfortable too. You don't want the slab getting too hot and overshooting the set temp of the room thermostats. Having more pipe in the floor just means your slab will heat more responsively ( quicker ) so a bonus rather than a problem imo. 

 

The 6 series from Vaillant is their system range, eg 630. The last 2 digits is the kw rating. The combi series are the 8 prefix. 

The 630 would be about right to maintain premium DHW recovery, bit with correct sizing of the cylinder you could go much less. If your tight on space then better to have the bigger kw and a smaller cylinder can then be replenished quicker. 

To answer the question about the buffer you need to know the kw requirements of your heating when it's up to temp and idling, eg an hour or two into any heating event when the house is maintaining the chosen temp. Look at your heating demand like driving a car. To get to 70mph off the slip road you boot the throttle to get up to 70 ( your set temp of 21oC for eg ) but then you take your foot off the floor to maintain that 'speed'. Your heating does the same, so your problem only starts when you ask the boiler to settle down to maintain the lower demand as it'll not like idling at anything lower than 9kw. At that point you'll drop out of the condensing range of the boilers flow and return temp and the efficiency plummets which is where the boiler is then 'modulating' to reduce its output to try and match the lower heat requirement. To maximise condensing efficiency you'll need to be up in the 50/55oC range, and maintaining it, to minimise running cost, but that would be impossible if your house isn't absorbing and dissipating the heat at the equivalent rate. The buffer would act like a battery, with the boiler pulsing much hotter ( max efficiency ~55oC temp ) water into the buffer, and the UFH then takes as much or as little as it wants to maintain the room temp. Look at that like going to the pub . You don't walk to the bar to take a sip of beer and then go and sit back down, instead you get the barmaid to fill a pint glass ( even though you don't want a whole pint right there right then ) and you take that and sit down, sipping from it as you require. 

If you were super thirsty ( house cold ) then you could neck the pint ( UFH wanting lots of hot water to get to the required room temp ) and then when your not gasping ( house is now warm ) you go back to sipping from the full pint glass. The barmaid ( boiler ) can fill the glass quicker than you can empty it ( correct sizing of boiler and buffer ) and she gets a rest between fills ( your boiler not short-cycling eg barmaid not running back and forth filling a half glass AS your emptying it ) 

That cycle of the boiler heating the buffer and then going to sleep is what will keep it in mac efficiency condensing range and keep the heating bill to a minimum. It'll also stop the short cycling issue that not having a buffer would create ( barmaid running back and forth filing a shot glass with beer ) which will fatigue the boiler. 

Any good ?

Edited August 23, 2017 by Nickfromwales

[s2sap]

On 8/22/2017 at 21:11, Alexphd1 said:

Do you know any good plumbers who would go on a day rate with a exact spec and diagrams to follow, with you providing material?

 

 

@Alexphd1 I don't but could investigate that option

 

 

 

On 8/23/2017 at 09:06, Nickfromwales said:

you need to know the kw requirements of your heating when it's up to temp and idling, eg an hour or two into any heating event when the house is maintaining the chosen temp.

 

@Nickfromwales I have attached SAP report. I hope to achieve a better result than this as we can prob get better values on air tightness and windows but didnt want to commit to for BC. Your beer analagy works brilliantly - I am much better at buying beer than building houses  

 

 

On 8/22/2017 at 22:07, ProDave said:

Do you have any SAP calculations or anything else to actually tell you what your heat input requirements will be? Without that you are guessing what size unit to fit.

 

@ProDave  SAP report attached

 

 

Thanks again for all the input

 

SAP_report_Redacted.pdf

Edited August 24, 2017 by s2sap