Ronski's Solar & battery DIY build with whole house backup

[Ron-ski]

So how long until you pull the trigger on a heat pump? That £7500 grants got to be burning a hole in your pocket!

Once I've got the the solar sorted I'll then look into the heat pump a bit more. We've got two local Heat Geek installers, so I'll see what they come up with and if their willing to work with me, prior to looking elsewhere.

I've already got some SWA run from the garage to the most likely place for the heat pump, it was an off cut, so seemed sensible to throw it in the ground ready for a heat pump.

When I re-plumbed the house back in 2005 I set every room up as a zone, so each radiator has its own feed and return to two central points with zone valves (its easy to remove the zone valves), although a lot of this is in 15mm plastic, but I'm hoping that will be OK. Our boiler will be 20 years old next year, so it would be prudent to take advantage of the grant and get it replaced with a heat pump.

 

[b0rn2sk8]

15mm plastic should be fine, I’ve got 10mm plastic although my heat loss is relatively low (under 6kw).

As you’ll say you’ll want to take the zone vales off and run it open loop but that’s a very easy change. Can you get your boiler below 50c with your current radiator set up?

Edit: what’s your primary flow and return pipe size?

 

[Ron-ski]

I've not tried lowering the CH flow temp, so I've no idea on that score. 22mm plastic feeding the upstairs zone valve manifold, and 22mm copper to the down stairs manifold.

Pretty much all of the radiators are over sized for the rooms, and 450 high, so worse case I could fit taller radiators, but also hoping they are sufficient.

Our gas bill last year was £780, which for a detached 5 bed house I think is pretty low. So ROI for a heatpump is unlikely for a long time unless I can really get the costs down.

 

[b0rn2sk8]

I've not tried lowering the CH flow temp, so I've no idea on that score. 22mm plastic feeding the upstairs zone valve manifold, and 22mm copper to the down stairs manifold.

That should be fine - they probably want to run 28mm from the heat pump to the cylinder location and onto where the CH pipes split between the two zones.

For my 4 bed detached (2002 build), I've got a single run of 22mm covering the whole house which T's off 10mm runs to each rad, all in plastic. It's not quite the worst case scenario but not far off, the main redeeming feature is the low heat loss.

Pretty much all of the radiators are over sized for the rooms, and 450 high, so worse case I could fit taller radiators, but also hoping they are sufficient.

Our gas bill last year was £780, which for a detached 5 bed house I think is pretty low. So ROI for a heatpump is unlikely for a long time unless I can really get the costs down.

I doubt there would be an ROI in reality for most people the running costs at a 50C flow temp are pretty much the same. However your average electricity unit cost is very low which makes things more interesting. Of course you can design a system to run at lower flow temperatures but you tend to increase retrofit costs as a result and sometimes its not practical due to existing pipework runs being too narrow.

I got a cheap big box installer to do mine (Octopus) and the cost to me for mine was only £3500 and it would have cost more to update the gas system I had to something modern (e.g. unvented cylinder).

I did consider a heat geek and a couple of other local installers but their pricing was higher and while they pitched a lower flow temp system with the associated lower running costs. I didn't go for it because it would have taken years to break even compared to Octopus when paying full whack for electric and as you know, my average unit rate is extremely low.

I could have replaced rads myself to get the costs down from the local installers but I just went with the big box installer in the end.

 

[Ron-ski]

My current boiler is a floor standing Worcester Bosch combination boiler (it was the biggest I could find back then), I'm hoping the tank will fit in the floor space that occupies, plumbing to the ASHP would be pretty straightforward once I've temporarily removed some kitchen cabinets, also the current heating plumbing goes off in two different direction from here. It's also central to all places hot water is required.