CH again - control systems.

[Mike Barnard]

Hi all.

Thanks to the posters who have helped out with my CH design in recent threads. I have 98% of the hardware in place now. I just need to finish the returns and pressure test it on Monday. [1] However, I can't decide on what controls to install now!

The boiler is a Worcester Bosch Greenstar R 35 HE plus, a condensing combi boiler.

There is no hot water tank.

Two zones in a small mid terrace house, one zone down and one up using Honeywell V4043H zone valves.

The boiler has a timer built in. The lounge has a Worcester "TR2" room thermostat which also has a four position switch with these settings...

• Constant on

• Automatic

• Constant off

• Frost protection.

So my questions are:

1. Should I use another TR2 for the upstairs zone or should I get one of those simple 'temperature only' thermostats? Or another mix?

1. Can you recommend a good junction box for bringing all the wiring together?

2. What cable should I use? OK, 1mm lighting cable is cheap and has the capacity but it's not very flexible. What about a softer round flex? ( I don't know the formulas for calculating the currents etc without spending lots more time searching online so it's just easier to ask those that already know.)

1. As usual, any good websites?

2. As an aside, anyone know where I can find a copy (free, of course!) of BS7671 the electrical regs? I know I can buy them from the BS site and the IEEE site but they're EXPENSIVE. I'm not using them for trade work so no one is gong to lose out on a sale... I just want to know the right way things should be done. I've tried searching for a torrent of them but no luck.

As usual, my great thanks for those who read this and bother to reply with sensible, practical advice.

Mike.

[1] For those odd people who care, I decided to put a TRV on the bathroom rail and install a bypass valve instead of leaving the rail open and no valve. The rail can get so hot it hurts otherwise.

[John Rumm]

I would suggest a programmable stat. That does the job of timer and stat and lets you specify different temperatures for different times of day. If the house heats reasonably quickly then a Horstman centaur stat (Screwfix) will do nicely. Or for houses with high thermal mass, then a optimising one like the Honywell RF67.

TLC do a range, just pick something big enough.

Multicore CH control cable (TLC again) is the usual thing. Current carrying capacity will be adequate for any normal system.

4. As usual, any good websites?

Lots of useful stuff covered here:

5. As an aside, anyone know where I can find a copy (free, of course!)

Does your email address work?

[Lurch]

On Sun, 08 Jul 2007 23:30:06 +0100, Mike Barnard mused:

Same as mine.

The TR2 is a low voltage sensor that is linked to the internal textdisplay controller on the boiler so will not directly control an external valve and you can only have one on the system, so take it out.

You want 2 programmable room stats to control the zone valves for the up and down circuits, and you want the switches in the zone valves to be wored to the external controls contacts in the boiler to turn it on and off.

Yep, a heating junction box.

Well, twin and earth\3 core and earth is for fixed wiring and flexible cable is for final connections so really you're stuck with that, unless you want to run SELV in for all the controls then you could use alarm cables.

Nope, any free copy will be illegal, unless you get sent a hard copy by someone very nice.

[Bob Mannix]

The TRV will not stop the rail getting so hot it hurts (until the room is warm)! Shut down the other valve so it is only open a crack is all that is required. You may also want the towel rail warm if the room is already warm. All in all the TRV is a bit pointless, if you just shut a valve so the rail only ever gets pleasantly warm/hot that's good enough.

[dennis]

Not true.. its a breach of copyright.. the copyright owner would have to sue for lost income.. and prove that he did lose income..unless the supplier of the copy was giving out lots of copies or selling them it is doubtful if anyone would bother let alone win.

[:Jerry:]

Which means it would be illegal, it might be civil rather than criminal law but it's still illegal.

[dennis]

No it might be illegal the copyright owner would have to prove it was and take court action to do so. He might lose and then would be faced with costs.

[TheScullster]

"John Rumm" wrote

I have two of the RF67s and found the "optimisation" feature a right pain. Ran the system for 3 months after install last October and they never did settle down. Ended up turning this "enhancement" off.

Phil

[Lurch]

On Mon, 9 Jul 2007 13:01:50 +0100, "dennis@home" mused:

But it's still illegal. Ring the BSI and ask if it's legal for you to sell copies of their documents as long as they don't pursue the purchasers.

[:Jerry:]

But that's also true in criminal law.

[John Rumm]

Yup, they suit some houses but not others it seems.

[Mike Barnard]

Hi. Sorry about the delay in replying. Just put a new phone extension in so had no internet for a while.

Thanks for the comments. I would definately not describe this house as having a high thermal mass! The more I look into cavities etc the more I see just how little mass this house has at all.

Ta.

something new each day.

to it...

Thanks, but I have a pdf of the 16th edition on my desktop right now. It's expensive, isn't it?

[Mike Barnard]

Nice boiler. Hot water runs at 14.5 l/min and it gives a powershower feel to the shower. Love it.

Grin. Now I see how identical they are.

See previous post about 5core CH cable.

Interesting point. First, as I'm not using it for profit, I don't care about this 'illegality'. Like it or not. If I were a qualified electrical engineer and were using this for profit I would feel differently. Probably.

The CONTENT of BS7671 is a British Standard. Just as there is a BS for Fire Extinguishers, for Crash Helmets, for just about everything. I do not expect to have to pay to know the content of a British Standard. *In my opinion* it is not a copyrighted item such as a fictional novel or a technical design for an item... it is a legal safety requirement. Therefore making people pay a lot of money for it is a travesty.

It is, of course, correct that people should pay a reasonable fee for the medium that the BS is supplied on, and pay for the work in producing same. A REASONABLE fee.

£50 for the book?

Rant over. :) Anyway, I don't need it now. I have a LEGAL purchased (used) copy. And I didn't pay much.

Thanks for all the insights.

[Mike Barnard]

Heh, true. I have put a bypass valve in anyway. Can't hurt and if I've messed up somehow maybe it'll save some damage.

[John Rumm]

An "ordinary" prog stat will probably do the job nicely then. The optimising ones are handy for buildings that need the heating on for a couple of hours to reach the target temp at a certain time.

its a newer site. It does not replace the FAQ, but adds to it. The wiki references the FAQ, but the FAQ has not yet been updated to point at it. You (and yes I do mean *you* or anyone else for that matter) can basically edit this one at will, so it is less peer reviewed and "controlled" than the FAQ, but at the same time much faster for getting collaborative articles in place, and also an easy place to stick bits of explanation that benefit for pictures.

Click the "history" link on any article to see who has written and contributed to it.

Just a scan, or one with searchable text?

I found the former, and recently got a good enough OCR package to produce the latter. (In my defence I might add that I bought and paid for the dead tree versions (BS7671 and OSG), so I am not depriving them of any revenue!)

The paper book, yup fairly - 45 & 17 quid ish IIRC. The official electronic version on CD (which to be fair does include lots of the other related books and not just the main one) costs hundreds. One of those things it would be nice to have, but not a justifiable expense in most cases I would guess.

[Lurch]

On Tue, 10 Jul 2007 11:51:20 +0100, Mike Barnard mused:

As mentioned, multicore flexibles are final connections only.

Although I do sort of agree with you, I'd imagine it costs an absolute fortune to produce the content as it's it's written by overpaid extremely literate morons.

No worries. :)

[John Rumm]

To be fair this is a bit of a grey area. Often for your final connections between (say) junction box, pump, cylinder stats, and valves etc, flex will be the most appropriate for these in most cases.

Bringing the call for heat back to the boiler may be better off done in cable, as may the connection to the wall stat.

Most heating devices have cable entry grommets and clamps designed for flex as well.