180L Cylinder

Foreverex

Just have British Gas come out for survey today. My space can only fit slim cylinder but BG only have 180L the biggest. He tried to convince me this should be enough for my 133m2 3 bed bungalow and 5 of us (3 young kids, but they will grow...). I think this is really marginal although we only have 2 bathrooms and it is about 20-30 minutes to heat up another tank for shower. 

Do you think I should go for other MSC provider or 180L should be ok? 

Thanks in advance. 

QrizB

We've got a 146(?) litre cylinder. It has been adequate for four of us in a 3-bed, 1 bath semi. We do stagger our baths/showers to make sure the.tank gets a bit of reheat time; I think four showers back-to-back would be too much.

NedS

You can read MCS guidance on DHW cylinder sizing here:

https://mcscertified.com/wp-content/uploads/2019/08/Domestic_HW_cyl_selection_guide.pdf

From the above, 180L is certainly within guidance. What size is the heat pump going to be, as this affects how quickly you can reheat the tank?

Ultimately, you can only fit a cylinder in the space available. We have a 160L slimline cylinder in a 3 bed property with 3 adult occupants, as that is all that would fit in the space available. We can reheat the cylinder hot enough for another shower from cold in around 20mins, so don't really see it as an issue. If we turned the hot water on when the first person entered the shower, it can largely reheat in the time it's going to take that person to finish up in the bathroom and the next person enter, so even if everyone wanted to shower straight after each other and emptied the cylinder, I think we'd still cope.

Rodders53

Get other quotes regardless!!

Do due diligence and a lot more reading on heat pumps and HW storage tanks. 

Lower temps = higher efficiency and that = less ability to mix down Hot with Cold in showers so more hot is needed...
Of course if you heat the water with immersions to 65C+ then it's the same as Gas or Oil boilers but leccy is more costly unless from solar or battery storage.

I'd also query that reheat time with the specifier... my OSO 210 litre takes 23 mins via it's 26.5 kW rated coil to reheat off an oil boiler.  Most ASHPs are rated a lot lower in kW output so must surely take longer (unless using 1:1 electric immersions to supplement the energy input).  (The above needs 9kWh to reheat the tank.  It also loses almost 2kWh every 24 hours despite being "well insulated".)

Exiled_Tyke

We have a 240l tank for three adults. I would say this is satisfactory.  One great advantage of a larger tank is that it can be heated to a lower temperature to provide the hot water that's needed. A smaller tank may need to be heated to a higher temperature and then mixed down to a greater degree. With an ASHP this is massively less efficient.   

michaels

We have 180l at 70C which just about does 5 showers so would need a lot bigger tank at 50C

Exiled_Tyke

michaels said:

We have 180l at 70C which just about does 5 showers so would need a lot bigger tank at 50C

Wow that's hot!  We get away with 43 degrees. And then run the legionella cycle over the weekend when I tend to need more hot water.  

NedS

The OP has said their available space can only fit a slimline cylinder, which by their very nature tend to be of lower capacity. They've already been offered a 180L cylinder (which seems reasonable), and I suspect you'd struggle to find a slimline model above 200L so realistically 180-200L is probably the largest achievable volume in the space available. The alternative is to find a bigger location or start knocking walls down.

Reed_Richards

My plumber made me steal a bit of extra space out of an adjoining bedroom in order to fit the cylinder.