How many zones ?!?

[RichA]

I am researching a new CH system and can't quite get to grips with how many zones to have...

Post refurb the house is expected to be configured as follows:

GF: kitchen/diner - UFH; sitting room - rads
1F: family bedrooms, bathroom, guest bedroom - rads
Loft: guest bedroom, ensuite, kids den - rads

Presume I need 1 zone for HW, 2 zones for GF. But what about 1F & Loft?

(a) 3 zones >> 1=family bedrooms, 2=guest bedrooms, 3=den
(b) 2 zones >> 1 per floor.
(c) 2 zones >> 1=family bedrooms & den, 2=guest bedrooms.
(d) 1 zone >> all rooms, control using TRVs.

What are the pros & cons of Zones v TRVs?

 

[RichA]

Having a rethink....

HW = 2 zones (Family 250L & Guests 125L)
GF = 2 zones (UFH & Rads)
1F & Loft = 2 zones (Family & Guests)

 

[ianmcd]

your installer will advise you on all of the above

 

[Malc]

Zones allow you to selectively heat some parts and not others. All CH+HW systems will have 1 "zone" valve if you like so you can have HW without having to have CH (e.g. in summer). Do you want to only run parts of CH? Remembering that if you say don't heat upstairs then downstairs will be cold unless you insulate the downstairs ceiling as U value between rooms is not very low, why would it be, there is no insulation between them and also there is good airflow too. IMO in a house zones are bonkers.

TRVs control the temperature in each room, but they can only do this if the CH is running so you still need a central stat (by central, somewhere that takes an average heat reading in order to control the boiler, you need a non TRV rad at this place too). You can get programmable TRV if you want fine control, for example to drop the bedroom temperature before you come to bed so it is cool enough to sleep in, but turn up in the morning to encourage you to get up when the alarm rings. You can also get programmable TRVs that are wireless so you can link them to home network and program from PC, tablet, etc..

You can do similar with zones so shut the upstairs off just before bed time so even though the TRV is wide open the rad is cold. Programmable TRV are more flexible though as you can have room by room control for those who like hot bedrooms and those that don't.

 

[muggles]

I've just specced a new install where every single room can be on its own individual zone, all controllable through an app or a panel on the wall. They can also be grouped together if required. How many zones you decide to have depends entirely on how much control you want. You can also, for example, set up IFTTT rules to turn the heating on in all the guest bedrooms when you turn the guest hot water cylinder on, so you don't have to do everything yourself. Ultimately the possibilities are virtually endless and only limited by your desires and your budget

 

[Malc]

Which system? What sort of cost?

 

[RichA]

Mid-level cost, mid-level control. Want to keep thinsg in perspective. i.e. I am on a budget, but, would spend extra for additional usabilty (assuming I was going to use it).

i.e. I don't expect to need to be able to set temperatures individually by room with an app.

Sounds like fewer zones, but use of TRVs would work better (albeit more manual when guests arrive).


I am also considering 2 HW tanks so that I can heat, say, 210L daily for family (4), and 150L occasionally for guests.

 

[Malc]

On the HW front you want to look at the cylinder figures. These will give the kWh loss per day. I would imagine that as HW cylinders get bigger there is little extra loss compare to the loss for 2 cylinders so you then need to consider how often you have guests. And the other issue is how often you need to heat the guest tank to kill off legionnaires which survives 20-50C. I would be inclined to having a single tank, maybe oversize for family, but with a fast reheat.

 

[muggles]

Consider a twin-coil cylinder - you can heat the top half when just your family are home, and the entire thing when you have guests

 

[RichA]

My contractor has suggested the following 'zones': HW, UFH, Rads.

He didn't think it was worthwhile separating the 2 floors as the temp on the upper floor will be dictated by heat rising from 1st floor. Does this sound like a sensible choice? or would I be better splitting GF & 1F?

I am thinking of going with Nest. How many would I need for both of the above?

Many thanks.

 

[muggles]

Is your UFH going to be all one zone? You'll need a Nest per UFH zone, plus one per rad zone, so one or two depending on whether you split the rest of the ground floor from the first floor or not. Worth looking at Honeywell Evohome though - it's probably a bit more expensive to buy than three Nests, but the advantage is that the pipework is much simpler (reducing install costs) and you don't need zone valves (further reducing costs). If you're buying a decent OpenTherm boiler, Honeywell's OpenTherm control is also much more advanced and more efficient that Nest's too

 

[RichA]

Thanks, I will look at Evohome too.

The UFH is one zone (kitchen/diner); the utility/study/hall/sitting room are rads.