Zoning with a combi

[jims45]

As zoning is now required in all new systems does this mean it is no longer practical to use a combi for a small installation,if viable has any one advice for setting out such a system.

 

[tackleburger]

Combis are for flats and one bathroom houses why would you zone that? If you are fitting them to larger dwellings, which I don't think is right anyway, then the same rules apply and zoning a combi is the same as zoning a system boiler no difference at all.

 

[GrahamM]

As zoning is now required in all new systems does this mean it is no longer practical to use a combi for a small installation,if viable has any one advice for setting out such a system.

New builds with a floor space over 150m2 must have this area split into 2 (zoned). There must be an independent means of control for each zone.
Why would it be not practical to use a combi? As long as the combi has been appropriately sized for the dwelling then this can be zoned. But if your dwelling is over 150m2 it is doubtful a standard combi will suffice.

Combis are for flats and one bathroom houses why would you zone that? If you are fitting them to larger dwellings, which I don't think is right anyway, then the same rules apply and zoning a combi is the same as zoning a system boiler no difference at all.

Since when are combis for flat and one bed houses? A larger combi will easily suit your average 3 bed semi. Its only when you step upto the 4 kids, 3 bathrooms in operation scenario, you need to think about adding a cylinder to the equation. You can still keep the combi though.

 

[tackleburger]

I said one bathroom properties. Properties over 150sqm are almost always going to have an ensuite and probably anadditional utility or wc. Adding cylinders to combis is ok but if you are using weather compensation you may well get conflicts with preheat controls etc. My view is if you require more hot water than one shower at a time combos are not the best solution

 

[powervan man]

New builds with a floor space over 150m2 must have this area split into 2 (zoned). There must be an independent means of control for each zone.
Why would it be not practical to use a combi? As long as the combi has been appropriately sized for the dwelling then this can be zoned. But if your dwelling is over 150m2 it is doubtful a standard combi will suffice.


Since when are combis for flat and one bed houses? A larger combi will easily suit your average 3 bed semi. Its only when you step upto the 4 kids, 3 bathrooms in operation scenario, you need to think about adding a cylinder to the equation. You can still keep the combi though.

The updated part L doc states that all dwellings now need a minimum of 2 heating zones contolled by a room stat apart form some bungalows and open plan dwellings ,e.g a 2 bed semi now needs to be zoned !

 

[GrahamM]

I said one bathroom properties. Properties over 150sqm are almost always going to have an ensuite and probably anadditional utility or wc. Adding cylinders to combis is ok but if you are using weather compensation you may well get conflicts with preheat controls etc. My view is if you require more hot water than one shower at a time combos are not the best solution

Apologies TB. Miss-read your post slightly. A decent combi installed correctly is sufficient for your average household, but as you mention stepping up into two bathroom territory is pushing it.
I know a few lads who have added an unvented to a combi system with no complaints.

The updated part L doc states that all dwellings now need a minimum of 2 heating zones contolled by a room stat apart form some bungalows and open plan dwellings ,e.g a 2 bed semi now needs to be zoned !

These regs are starting to kick the backside out of it! They are becoming pathetic.
What is wrong with your room stat and TRV's? Is that not enough control for your average household?

 

[AWheating]

maybe the guy who updated the regs has shares in a controls company??

on a normal combi install how much would be saved in energy compared to the extra cost of the install? The simple adjustment of a trv costs nothing.

 

[tackleburger]

maybe the guy who updated the regs has shares in a controls company??

on a normal combi install how much would be saved in energy compared to the extra cost of the install? The simple adjustment of a trv costs nothing.

I try to fit all my systems with weather comp and don't bother with trvs downstairs in the main living areas. Upstairs good quality trvs are all that's required. On Larger systems where possible I'll zone it and won't fit the trvs with weather comp you don't need them

 

[AWheating]

sometimes its hard to convince customers they need to pay for some trv's, try telling them they need to zone the 3 bedrooms.

 

[tackleburger]

I know. I'm not sure that's right though Zoneing everything. I would check part L if I was you. I am in Scotland not affected by that. I had a quick look it just states meeting u values etc.

 

[jims45]

Thanks for your responses guys, according to OFTEC technical, all installations (apart from some open plan) have needed to be zoned since oct 2010.
As a newbie I was unsure, but it seems nonsense to me as you are increasing system volume with extra pipework and also adding extra components the manufacture of which must also create polution.
Do the people dreaming up these regs actually fit systems

 

[stevetheplumber]

Thanks for your responses guys, according to OFTEC technical, all installations (apart from some open plan) have needed to be zoned since oct 2010.
As a newbie I was unsure, but it seems nonsense to me as you are increasing system volume with extra pipework and also adding extra components the manufacture of which must also create polution.
Do the people dreaming up these regs actually fit systems

its another way to send people into the arms of unregistered installers the more us rgi's have to fit the easier and more profitable it becomes for the un registered cowboys in the same way that raising tax on cigarettes and booze makes smuggling more profitable

 

[GQuigley67]

I've got a question regarding this scenario, when zoning with a combi say zoning upstairs and downstairs would you fit 2 zone valves and wire them to room stats and it will be the room stats that control the zone valves ?

 

[Mrs Tara Plumbi]

maybe the guy who updated the regs has shares in a controls company??

....

I have suspected this for many years,
since it became almost mandatory to have TRVs all over the place whether you wanted them or not. Adding a whole load of cost to installation and not always any benefit. Some people will NEVER want to turn the TRVs down in some rooms but they still had to have them.
And as said it is questionable whether the (theoretical) saving in cost of gas will ever cover the cost of installing some of these controls.

 

[Kimou]

I'm not even sure that TRVs are effective in upper levels. As heat rises they will shut off before the room gets warm. Am I right in thinking this way?

 

[AWheating]

you are correct, but if the trv does not open then it means the room temp is at or above its set level and the rad does not need to be on.

 

[AWheating]

http://www.worcester-bosch.co.uk/cache/file/23/changes-to-part-l-affecting-new-heating-systems.pdf

worcester bosch tech bulletin on zoneing

 

[Blackcatgas]

Ive just done a new build, Ive run a viessmann vitodens 100 combi to do the hot water in the ensuite, kitchen, and wc and then run the heating flow and return into 3 , two port valves which heats the 150 liter unvented cylinder for the main bathroom, the upstairs rads (wall stat upstairs) and then to a underfloor system downstairs with individual room stats downstairs.
I did this a few months ago when I wast even aware of the new zoning regs.
The advantage of this is that the customer can have instant hot water when they want it and when demand is needed the adbvantage of an unvented system.
Iam so big and clever, I dont understand why girls dont want to talk to me.

 

[AWheating]

i have fitted simular systems a couple of years back, combi just feeding kitchen an utility on hot side and then zoneing to a cylinder and two heating zones on heating side. with the secondary return and gas aswell is very hard to get all the pipework fitted and lagged in the space available under the floor.

 

[GQuigley67]

So would I be ok with a Time Clock, 2x 2 ports wired to room stats ? for Zoning a Combi

and for wiring them to the combi should I take the flexi's from the switched spur to the 2 zone valves, then from the zone valves to the room stats ??

not had to zone a combi before

 

[Blackcatgas]

So would I be ok with a Time Clock, 2x 2 ports wired to room stats ? for Zoning a Combi

and for wiring them to the combi should I take the flexi's from the switched spur to the 2 zone valves, then from the zone valves to the room stats ??

not had to zone a combi before

your basicly running a combi as a system boiler, just think of the heating flow and return as primary flow and returns to be run from the boiler to 2 , two ports.

 

[stevetheplumber]

the combi is fired by the aux switches in the motorised valves the valves are powered from the room stats you cant use dedicated stat terminals from the combi

 

[GQuigley67]

anyone got any wiring diagrams I can have a look at ? ? or a link ??

 

[Bernie2]

Just a thought!

What about condensing combi's?

Many require a large unregulated rad in some part of the system to drop the return temperature the surface area of by pass circuit not being big enough. Bit of a nuisance really.

But if you zoned the system you would need an ungoverned rad in each circuit for it to condense properly. A bit more of a nuisance for the customer.

 

[AWheating]

Just a thought!

What about condensing combi's?

Many require a large unregulated rad in some part of the system to drop the return temperature the surface area of by pass circuit not being big enough. Bit of a nuisance really.

But if you zoned the system you would need an ungoverned rad in each circuit for it to condense properly. A bit more of a nuisance for the customer.

you would require an ungoverned radiator in all zones for correct operation of room stats