Combi UVC or TS

[Tiny]

Hi

I am working my through planning a refurb and extension and have arrived at the heating system and DHW. Plans viewable at https://www.dropbox.com/sh/d08qpdimnntxh7g/AABxGcrJOqAJJbgrLYXuB4Ega?dl=0

Currently only two of us and one bathroom and we have managed with a gas condesning combi boiler, we have a thermostatic shower and it has good pressure. However once the extension is completed we will have three showers plus a bath. So what is the best solution that will allow at least two showers to run and a hot tap or washing machine/dishwaher simultainiously?

Plan is to replace all the radiators with Jaga Strada low H20 of various sizes.

Is a TS or a UVC the best solution?

should I pipe it in Hep20 and radially with a manifold?

I would like to have four or possibly five zones, is a digital thermostat in each zone and zone valves the way to go

or should I just fit TRV to each rad

ideally would like a degree of remote control as house will become a holiday rental for part of the year and figured I could use the Heatmiser thermostats and wiring centre

any suggestions gratefully received as I am drowning in a sea of choices, plumbing being just one! 

I set off thinking houses where simple

thanks in advance

[Alexphd1]

Hello & welcome. Nice looking project.

Just throwing in another option... why not a sunamp heated by a gas system boiler? Can size it big enough for the highest demand but only use what you need  when just two of you are in with v little heat loss. best of both worlds!

lot of options for zones internet controls etc but you need something simple enough for joe public to use... most people i know still dont understand how a TRV operates and even more are not interested.

Can i ask why you plan to use the jaga low water radiators, i have not came across them before.

[Nickfromwales]

Late to this one sorry. 

A bit tricky to get high capacity / high flow DHW without some serious grunt. 

A large TS will deliver 20+ Lpm, and, if boltsrered by a whopper of a gas system boiler, will provide that nigh-on constantly. 

An UVC will do the same but would have to be sized bigger as you can't hear an UVC as quickly as you can heat a TS. 

I fitted a 440L TS for a customer and complimented it with a 300L cold mains accumulator. I had 2 showers running flat out, plus plenty enough DHW flow to open both the kitchen sink hot and the cloakroom hot tap, all simultaneously. That flow drops off as the accumulator depletes so sizing both accordingly is an important design consideration. 

"You get what you pay for" etc etc. 

Forget a combi, that's obviously not even a consideration, and if your stuck for space you could go the SA route, but they're a pretty penny compared to a TS.

You can now, I believe, ask @AndyT for prices for a dual port SA setup that would be comparable to the above. The dual port have two separate heat exchangers so one in for primary heating flow / return, and another for potable ( DHW ) production. 

The price premium is significant, but with no G3 consideration and time / labour expended on routine maintenance ( draining down to check the EV pre-charge which should be done every 6 months ) you'd have paid for one in ~ 10 - 12 years which is a good pay-back IMO. 

Decisions, decisions  

[Tiny]

Hi Alex

Thanks for your reply, the Jaga radiators are lightweight, low water, but more importantly for us, heat really quickly. The Sunamp looks an expensive way of solving the issue. There must be plenty of houses with two or more showers. Am I on the right track with the heating controls and set up do you think

 

[Tiny]

Hi Nick

Thanks for your reply, I am currently staying in a mates house in France for a few days, it has a UVC of 200lt heated electrically. It appears to handle two showers running and does six people showering every evening. I appreciate it has all night to warm up again before being required again.

If I fit a large TS could I run the radiators and DHW from it? I would like to ensure that the boiler ret temp is such that it condenses. How do I ensure the return temp is correct?

The total whole house heat loss is 11.3kw

I was looking at Emmetti manifolds with electrothermic heads, could I use Heatmiser thermostats and wiring centre with it? what do you think

Trying to build an efficient, responsive system as simple as possible

Sunamp looks expensive and we have no solar panels at the moment, and not much sun!

 

 

 

[CC45]

Got a Wunda manifold & some 15 to 16mm adapters into rads.  Will get it plumbed within  the next month or so.

[Nickfromwales]

On 22/03/2018 at 20:34, Tiny said:

If I fit a large TS could I run the radiators and DHW from it? I would like to ensure that the boiler ret temp is such that it condenses. How do I ensure the return temp is correct?

A TS will do a multitude of things, specified by its design. These are almost always a bespoke procurement but not very costly considering. 

A large TS will do space heating and DHW without issue, so no problems there. Just order it with the appropriate tappings and you'll be sorted. 

The cylinder stat tells the boiler to fire, so just set the boiler flow temperature on the boiler control panel to the temp you want, which will be the same every time it fires. That way you can dictate the flow and return temps to maximise on condensing efficiency.

On 22/03/2018 at 20:34, Tiny said:

Sunamp looks expensive and we have no solar panels at the moment, and not much sun!

They are in comparison but the equation requires a bit more appreciation of what the SA unit brings on returns and running costs.

Annual G3 inspection will set you back around £120 a year. 10 years is £1200. Plus you'll have the inconvenience and time wasted meeting an engineer, making the appointments etc, and the discharge pipe runs. Plus, add in the extra energy losses which you pay for. 

An UVC or TS will cost you its original cost every 10 years. A SA will earn its keep. 

Also, size vs energy density a SA is around 1/3 - 1/4 of the physical size of its cylindrical counterparts. A big TS is cumbersome, a SA can fit where a slimline dishwasher would. 

Im not blowing smoke up the arse of SA, but its hard not to promote them when they have such a good place in the market.  

I remain 100% impartial in my comments on BH, and these are my personal opinions. If capital outlay is a factor then simply choose a cylinder as that's the cheapest route to a system that will suit your immediate requirements