Help,where do we site heat pump and all the gubbins?

[Nickfromwales]

17 hours ago, Dave Jones said:

make room for at least 2 tanks unless you enjoy cold showers.

Are you typing this from the pub again? I thought we agreed nothing until after 11:00!!

 

One tank is ample, you just size it accordingly, ffs. 🙄

[Nickfromwales]

@Selfbuildsarah

How many people in the house, and how many bathrooms / baths? Remember that the second you lower the volume of premium heated water in the hot water cylinder the cylinder stat will kick in and fire up the heat pump at 100mph to reheat it. This will happen before you turn the hot tap off most likely, so as you are consuming hot water it will be getting reheated simultaneously. For an ASHP and anything more than 2 occupants you should go to a 300L cylinder IMO.

 

You asked if the pic you referenced was a job where UFH was installed, answer is yes. See the 2 manifolds lower down in the pic R/H/S.

 

How many metres of pipe, exactly, will be needed to run the ASHP to the cylinder as you wish it to be done? 15-20m is no real world issue, but will likely need a second pump on the return to compliment the one in the ASHP on the flow.

[SteamyTea]

19 minutes ago, Dave Jones said:

10l flow is pathetic

As usually, you don't understand the very basic physics.

That is the flow rate of the hot water only (in the example I gave) it then gets diluted with cold to make it a usable temperature.  So the flow rate from the tap will be higher.

And anyway, 10 lt/minute is a pretty good shower, you don't get twice as clean by doubling the flowrate.

22 minutes ago, Dave Jones said:

expensive to heat on demand in daytime so not a good idea

While I agree with this, for the occasional times that you have to because of higher usage, it is cheaper than having a secondary cylinder.

24 minutes ago, Dave Jones said:

The only thing going for ASHP over a gas boiler is its cheaper to run, everything else is a negative.

Not much difference, but are you not fitting an ASHP in your place?

[Nickfromwales]

@Selfbuildsarah

Also, contact Trevor at Cylinders2go and mention my username and the forum for a discount on the cylinder. Telford stainless has a lifetime warranty too, and plenty on here have used them.

[PeterW]

@Selfbuildsarah you don’t need that much space and you can “stack” things such as the expansion vessels on top of the cylinders. First off, need to know how many showers etc you have - 10l/min is a pretty decent shower and is the maximum under the G2 water efficiency regs if you’re required to achieve that anyway.

 

With an 70/30 of hot to cold from a 300 litre tank at 52°C, you’re at around 40 mins of shower flow before you get a cold shower. Take that tank to 72°C and you’re adding around 18 mins additional flow which is actually a fair amount. 82°C and you’re over an hour at 65 mins of capacity, and this is from a 300 litre UVC with 90% usable capacity.

 

300 litre UVCs are pretty easy to get into surprisingly small spaces - the Telford one is 660mm diameter and that’s not far off the same footprint as an ordinary fridge freezer. Telford custom make their cylinders at no extra charge with all ports and connections where you want them too so they are easily installed.

 

I’ve designed variable flow installations with domino tanks using multiple UVCs but that’s for buildings such as B&Bs who want flex but limited heat loss when rooms aren’t in use and the 2 variables are always capacity and temperature - all depends on the need, and proper design from the outset.

 

[SteamyTea]

It does seem odd to me, but then I am odd, that people obsess over something that we spend around 1/50^th of our time doing.

If a DHW system has limitation, learn to live with them, 7 million people with E7 manage it.

Edited May 28, 2023 by SteamyTea

[Dave Jones]

1 hour ago, Nickfromwales said:

Are you typing this from the pub again? I thought we agreed nothing until after 11:00!!

 

One tank is ample, you just size it accordingly, ffs. 🙄

its just not for a family with 3 teens. Not interested in micro showers and cold water!

[Dave Jones]

1 hour ago, SteamyTea said:

As usually, you don't understand the very basic physics.

That is the flow rate of the hot water only (in the example I gave) it then gets diluted with cold to make it a usable temperature.  So the flow rate from the tap will be higher.

And anyway, 10 lt/minute is a pretty good shower, you don't get twice as clean by doubling the flowrate.

While I agree with this, for the occasional times that you have to because of higher usage, it is cheaper than having a secondary cylinder.

Not much difference, but are you not fitting an ASHP in your place?

 

i am but working round all its limitations to minimise the negatives as much as possible. looking to be 10 - 15x more expensive to install than a gas boiler.

[Nickfromwales]

10-15x if a retrofit into an existing poor / leaky dwelling, not so if a new job?

7 minutes ago, Dave Jones said:

Not interested in micro showers and cold water!

Simple. Then you fit a 400L UVC. Incremental price increase is WAY less than buying and installing ( and finding a home for ) a second UVC, still uses the same footprint, and will be ample. I only put a 500L in for a family with 4 generations living in a massive, multi-bed / multi-bathroom house. Once blended down to shower temps that's a LOT of hot water.

A "guest" switch gets fitted on any of my jobs where the house is 4 beds or above. One tap of a button and you get a 15/30/60/90/120 mins boost to either 1x or 2x 3kW immersions for duress DHW eg there's a wedding / other and the house is fully occupied with more occupants than rooms. Constant DHW with that lot going + ASHP in DHW mode. 

[SteamyTea]

12 minutes ago, Dave Jones said:

looking to be 10 - 15x more expensive to install than a gas boiler.

That is because you don't know what you are doing.

[JohnMo]

It's not that cheap to run making DHW, with an ASHP, its cheaper than direct electric heating, by a margin of two and bit. But preheating a single big cylinder to 50 or so via ASHP and topping up to 60+ via an immersion isn't much worse than a heat pump. 

 

Plus a big single cylinder of x capacity had a daily heat loss that is way less than 2x smaller cylinders of half the capacity each due to the extra surface area. Plus you also have parasitic losses of the piping x 2.

[Nickfromwales]

33 minutes ago, JohnMo said:

But preheating a single big cylinder to 50 or so via ASHP and topping up to 60+ via an immersion isn't much worse than a heat pump. 

What most with an ASHP + PV do anyways. When you add into that equation the stop-start of the ASHP, plus possible freezing, plus the moving parts, and then work out the reduction in longevity of all the kit outward of the cylinder, the maths really begin to shift further away from heating north of 50-55^oC via the HP. Immersion is 100% efficient, zero moving parts, and is cheaper than shoplifting to replace.

[TonyT]

Plus you can use the immersion on a night time tariff, maybe 3 times cheaper than day time electricity.  Plus 1 for above good to give the heat pump a break with the cheap immersion