Planning new boiler & heating zones

[jpdw]

Hi,

As soon as it gets warm enough in 2008 to turn off the CH, we'll be getting a new boiler to replace the 10yr old one that was fitted to the house before it was extended & had a loft conversion.. ie it's old, inefficient, noisey and undersized.

Originally we were looking for just a boiler replacement (we know it'll be condensing) but I am also now thinking of zoning the house and also improving the way the conservatory rad is plumbed in (currently not very well IMHO). It would make sense to do this all at the same time, so I'm trying to work out what I want and whether it's realistic without re-fitting all the pipework (cost of which could outweigh the benefits).

At the moment, the conservatory rad is before the pump. I'm no plumber but this seems wrong to me. BTW... we normally have the valve on this rad OFF. The new boiler will have integral pump, so at last the flow to this rad would be pumped. I'd add either a zone valve or electrically driven rad valve so that the conservatory heating can be easily switched "on"/"off" from inside.

A quickly drawn sketch of the current system may help explain...

The boiler is in the conservatory (next to the conservatory rad) whereas the tank (unvented) and CH zone valve are in the bathroom probably 10-15 metres distance along the circulation pipes.

I would then get the 3 floors split, 1 zone each with local thermostatic control on each floor & TRVs on some of the individual rads. The pipework looks like it only needs minor changes to split ground & first floor.

My current thinking is relatively small changes to modify so it's like this...

So my first question is whether this arrangement of 3 CH zones effectively in parallel with the HW would work? Presumably the switching on the HW valve can be used to add HW prioritisation if needed ?

But my main quesiton is that this effectively gives 5 heating zones, where 1 zone (conservatory) is very close to the pump/boiler and the other 4 zones are some way away.

I would appreciate if anyone has any comments if this can be done achieved like this or whether the conserv. rad flow would have to come off at the same point as all the other zones.

Thanks... & happy new year to everyone !

 

[gas4you]

I always prefer to have all my zones valves in one cupboard (airing) so this then becomes the nerve centre of the heating system and is neater as well. I would also want to have all the returns commoned into the airing cupboard as well, to eliminate any back feed on them.

I would assume also that you will need 28mm flow and return from the boiler to the airing cupboard.

 

[jpdw]

The airing cupboard already has the existing flows (because the boiler will be where the existing one is), though I'm not certain if they are 22mm or 28mm. They do already go back, same size, to the boiler. I was hoping the flowing pipes would need no changes as that obviously increases disturbance & cost.

Whilst having all valves in one place is much neater, the extra 10-15 m of copper needed to run back from the airing cupboard to the conservatory rad would be a real pain .. again, more disturbance and the extra pipe would need more holes through joists, through the outer wall to the conservatory etc,.. I'm prepared to sacrifice this neatness so long as it'll still function okay. Besides, there will be a boxed in section below the boiler where I would hide the conservatory zone valve.

 

[gas4you]

I would be concerned that there is a small risk of the conservatory rad return backflowing by gravitation to the returns of the other rads in your current proposed set up.

 

[jpdw]

So if we had a return out of the conserv rad back to the common return in the airing cupboard then we could still take the flow to the conserv rad from "close to" the boiler? (this would mean 1 extra pipe back to the airing cupboard and not 2).

 

[jpdw]

is there any other (sensible) way to eliminate possible back flow?

it's just that having the conserv rad 2m from the boiler, it seems such a "win" if there is any way to avoid taking it all the way back to the airing cupboard!

 

[gas4you]

You could fit a non-return valve in the return to the airing cupboard as a last resort.

I don't like them as it is something else to go wrong and stick at a later date.

If you do use one, keep it accessible with a gate valve each side.

 

[jpdw]

If you do use one, keep it accessible with a gate valve each side.

Dont you worry ... accessibility is definately an important part of the brief! The existing CH zone valve died during the freezing spell in december. Took me 30 minutes just to take the motor head off because its mounted with the fixing screw just 2 inches off the floor and behind 2 other pipes. Putting the new on etc took an hour thanks to the stupid location. Once the existing pump and filling loop have been removed (will be in the new boiler) there'll be space to make everything neat and tidy....

 

[bengasman]

You will need to repipe the conservatory rad as building regs require separate control for conservatory.

 

[jpdw]

You will need to repipe the conservatory rad as building regs require separate control for conservatory.

Hi Bengasman,

I've read up a little on needing conservatories to be separately controlled, but are you saying that "separately controlled" required 100% seperate pipe work from the boiler to the rad & back ?? Surely not??.

The reason for wanting to zone off the conservatory is to provide exactly the effect that I thought the building regs were getting at -- not wasting heat unnecessarily on a room that's very-un-thermally-efficient.

...At the moment, the conservatory rad is before the pump... .... I'd add either a zone valve or electrically driven rad valve so that the conservatory heating can be easily switched "on"/"off" from inside....

To elaborate on what I was intending, it was either a zone valve on the flow to the conserv rad or an electrically driven TRV actuator (similar affect ... power on, water flow; power off, water doesn't flow). The intention is that the conservatory will have it's own thermostat and other than frost prevention, the valve will only be turned on if a big switch in the kitchen is enabled ( with glowing neon to remind us we're heating the conservatory). Aside from saving the planet & complying with building regs, I want to minimise heating the conservatory to save paying ££££ to the gas company

I thought what I was intending would more than satisfy the b-reg requirement? (does it apply to modifications of existing systems anyway?)

 

[bengasman]

I will probably be the last one to say that building regs are fantastic and logical, but they are what they are; up to you to follow them or not.
Fact is that your system is currently not of great design and unless you spend a lot of time and effort getting to know all the ins and outs of central heating, you might let yourself in for a lot of future costs if you diy this project.

 

[tabs]

Electically driven trc actuator -tell me where to get one of these please. Or your not talking about the honeywell rf trvs are you?

 

[gas4you]

I looked into this conservatory carp, and it appears that anything under 30m2 doesn't have to conform to these regs.

It is about outside rooms generally rather than conservatorys specifically.

 

[jpdw]

I will probably be the last one to say that building regs are fantastic and logical, but they are what they are; up to you to follow them or not.
Fact is that your system is currently not of great design and unless you spend a lot of time and effort getting to know all the ins and outs of central heating, you might let yourself in for a lot of future costs if you diy this project.

Bengasman, I agree with you on regs -- good or bad they are there & unless we move to another country (and different regs) they are they to be adheared to.

When our plumber looked at the boiler a few months ago he didn't mention that we couldn't have a rad in the conservatory - or maybe I'm mis-reading your advice?... though at the time the pipework was covered & it was not clear exactly the current way the rad was connected.

Going back to the regs a moment, I thought the building regs required the conservatory heating to be separately controllable -- are you saying that a zone valve or acutated TRV does not provide sufficient ability to isolate ?

 

[jpdw]

I will probably be the last one to say that building regs are fantastic and logical, but they are what they are; up to you to follow them or not.
Fact is that your system is currently not of great design and unless you spend a lot of time and effort getting to know all the ins and outs of central heating, you might let yourself in for a lot of future costs if you diy this project.

Oh, and dont worry... I'm not going to DIY the project ...! Too much risk we'll have a swimming pool instead of a conservatory!

The plumbing will be done by a pro, but in the context of a bigger bit of refurb/redecoration. I'm trying to work out what we want but also with some realism about what can be done -- so we can have a written-up scope before we start (I'm a project manager by trade, so making it up as we go along is supposed to be something I avoid )