CH Zones again.

[Mike Barnard]

Hi.

I'm making a new thread because the other one was getting pushed down the list and lost in the background, and it has raised some new questions for me.

I have now decided to zone; 2 zones, 1 upstairs and one down. Many thanks to the posters who have given advice. The house is too small and tight to put more pipework in than this. Now my remaining questions are...

1. Can I use a common return? (There was an answer in the previous thread but it made no sense to me.) If zone 1 is operating and zone 2 isn't, can there be a problem with using common returns?

1. Can you reccomend a RELIABLE valve to use for just two zones?

2. What about 'primary' rooms and rads without TRV's? As I understand it, the rad in the primary room (the room with the controls in, yes? Thats the open plan lounge in my house) should have no TRV. Do I need a primary room in each zone? What if the controls are in the upstairs hall which has no rad?

1. Websites? General CH design as well as zoneing.

Again, thanks. It's help from people like you that makes my home better! :)

[Roger Mills]

It's good practice to combine the returns from all the rads in each zone before combining the two composite returns. Otherwise, there's a risk of reverse circulation through the zone which is supposed to be off.

Is there also a HW zone (although ISTR that it's a combi boiler, in which case there won't be)? In any case, go for an S-Plan solution, with a separate 2-port valve for each zone rather than trying to do it with a single 3-port valve. Any of the well-known makes (Honeywell, Danfoss, Drayton, etc.) should be ok. Make sure you get ones with secondary contacts which close when the valve opens - which you will need for switching the boiler on whenever either or boths zones call for heat.

You need a room thermostat (preferably programmable if you want to heat the

2 zones at different times) in each zone. Each thermostat controls its respective zone valve which, in turn, controls the boiler and pump. The radiator which heats the space whose temperature is sensed by each thermostat should *not* have a TRV - but should be fitted with two lockshield valves so that it can never be turned off. If a zone's thermostat is not very near to a radiator, it must at least be somewhere where the temperature is *influenced* by that zone - otherwise the control system won't work.

You could do a lot worse than starting with the heating section of the DIY FAQ at

[TheScullster]

"Mike Barnard" wrote

The honeywell 4043H is as good as any. Check out

and click on the "Yes" next to S plan documentation. Unfortunately they still haven't created guide for S Plan +. Agree with other posters about commoning up returns. The plumbers who recently dual-zoned my system commoned all rads onto their respective returns, then brought all three return mains (2 heating zones and one hot water) together at a common point. (The DIY bit was that I specified the system with help from this group and also replaced most rads prior to the upgrade)

Phil

[Tony Bryer]

To stop the possibility of reverse circulation you need to bring all the zone 1 returns together before linking to the common return, do. zone 2. If (say) the return from zone 2 passes across two different returns from zone 1 there will be a pressure difference between these points and a portion of the flow will go up one return, through the rads, along the flow (in the reverse direction) to the second rad and back along its return.

[John Stumbles]

(if it doesn't answer your questions please let me know how it could be improved!)

[:Jerry:]

If he knew that he wouldn't be asking the question in the first place ! Duh....

[fred]

In article , Mike Barnard writes

If you see an answer that you don't understand then the original thread is the place to query it rather than starting a new thread.

Honeywell 2 port valves (22mm) as they can be obtained at reasonable cost from discount outlets and replacement parts are readily available in the event of failure. They can still fail so don't bury them behind nailed down floorboards.

Yes

Controlling upstairs rads from a stat in the hall where there is no rad and where heat flow could be restricted by closed doors would be a mistake, if you chose not to split the upstairs then you need the stat to be placed on the cold side (bed)room and the TRV on the warm side (bed)room.

The general rule is that that the (global) control should be in the slowest room (area) to heat up and the fastest room (area) to cool down, in that way the secondary areas should be neither too hot nor too cold.

Don't worry if you have difficulty understanding these concepts as few CH technicians will have a better grasp.

[Mike Barnard]

No, its a combi and I have no HW tank. Saved me the space the cupboard was taking.

OK, googleing for S plan now sir! :)

OK.

So, yes, I need a primary room in each zone. :) Thanks.

Thanks for taking the time, I really apprecieate it.

Mike.

[Mike Barnard]

Will do, thanks.

Oh. . Er, I see.

Agreement, I like it! :)

Understood. Yes, really.

As before, thanks I really appreciieate the effort you have all given.

Mike.

[Mike Barnard]

Got it, thanks. Really apprecieated.

Mike.

[Mike Barnard]

Looks neat. Haven't had the time to look at it in depth, but thats a job for the weekend.

Many thanks.

[Mike Barnard]

I'm a fair judge of screen colours. Sometimes.

Mike.

[Mike Barnard]

Been looking at my tight layout. I have NO idea where I'm going to put the valves.

No, there's no airing cupboard. The walls in and around the boiler are tight with 'stuff'. The bedrooms are full of fitted units.

Anyone everput then in the ceiling void with a small trapdoor for access? It's about all thats left.

Mike.

[Mike Barnard]

"For details on Zoning, see Practical Application Guide No. 117"

"117 Zoning. Soon"

Heh, just my luck.

[John Stumbles]

I've had to replace one there :-(

[Mike Barnard]

Touche.

Noted, thanks.

Also.

Noted.

Now, these are the sort of rules that never seem to make it into websites. Massively important bit of info. Heh, maybe it should go into the DIY Wiki (if it's not already) mentioned above.

Understanding is OK, it's just the working it out to start with. So I could use either the bathroom or bedroom 2 as the primary room as they're both north facing and they are very cold rooms.

Bathroom: Gets visited most often. Gets wet morning and night.

Bedroom: 5yo Sons room. Out of use 95% of day.

I presume part P precludes the controls from being bathroom based. Shame.

Thanks.

Mike.

[Lurch]

On Fri, 29 Jun 2007 20:20:16 +0100, Mike Barnard mused:

Loads of people have, but i'd usually call it under the floor rather than above the ceiling.

[Andrew Gabriel]

I've put one on top of a kitchen cupboard, which is not visible unless you are 7' tall. I've seen them installed in kitchen cupbards too (more often, the cupboard is fitted around the plumbing, and can be completely removed for servicing).

[fred]

Sorry for the delayed reply.

In this case I'd probably run the bathroom off the live backbone so that it comes on whenever the boiler fires ie any heating or hot water demand. Use a TRV to limit the temperature and turn it off completely in summer as required. Although it doesn't appear to make sense to control from your young son's room, if that is the cold side of the house then it is probably the way to go (for the upstairs)

Even if it doesn't, it's unlikely they'd last long in a humid environment. The ones I have looked at preclude that kind of placement.

[Mike Barnard]

Heh, no one waiting. Just grateful for any help.

What a splendiferous idea. I think I can mix that into the plan.

Why not? As you say, its the coldest bit. Also it's over the kitchen so closer to the boiler for cable running.

And the varying tempratures switching it off and on at odd times I suppose. Shower on and windows closed or loo used and window open! :)

Thanks for the ideas.