I want to know how combi boiler clocks/timers work...

[Dan Gravell]

Mine recently stopped working, that is to say it works for a bit, then stops, then works for a bit.

"Works for a bit" means that the clock is audibly ticking, and the mechanical clock rotates. "Stops" means neither of these things happen.

To my untrained eye it seems the power is running dry on the clock. The strange thing to me is that I thought boilers were plugged into the mains, so how could it run out of power?

Now an admission: I made a post on this yesterday, but I think it was over specific in terms of detailing the manufacturer (Sime) etc. What I'm looking for now is just some general guidance on how these things work, as I'll probably get someone out to do it, and I don't want to get stung. I just spoke to a guy who was very vague, talking about some piece of kit between the power and the clock, which could go wrong.

Thanks, Dan

[Christian McArdle]

Set the timer to be on 24 hours a day. Replace your room thermostat with a programmable type. Then it doesn't matter that your clock is knackered, and you have the heating controls in the lounge, where they belong and all the advantages of a programmable thermostat, such as selecting a specific temperatures for different times of day.

This presumes that the same fault doesn't prevent the 24h option from working.

Christian.

[Dan Gravell]

Do you mean a wall hung thermostat? The only thermostat I have is one on one of my rads (in my lounge). I don't think I have some master thermostat. There is a control on the boiler which seems to make the boiler turn on more often, but none that stops it turning on at all.

It works fine when it's manually switched on.

Thanks a lot, Dan

[Christian McArdle]

Well, spend your money having one installed, rather than fixing the clock. It will not only make the timing work, but will save you a fortune in gas, as currently the boiler will be on for the entire time that heating is selected on, not just when the house is cold. As it appears you don't even have widespread TRVs, the house will likely overheat, too, causing really quite appalling energy efficiency.

Christian.

[Dan Gravell]

Thanks very much! I'll certainly have a look into this.

Dan

[Christian McArdle]

P.S. Also, put TRVs on all your radiators, too, except for the room you choose for your room thermostat. I prefer the lounge for this, as you get tightest temperature control in the room selected. Some choose the hallway, as it is often the coldest and most underheated room, so the heating stays on until all rooms are hot. However, you mustn't choose a room with alternative heating (such as a fireplace or gas fire) that is used frequently, as it will fool the heating into shutting off, making the rest of the house cold.

Doing all the above will not only save you (and the earth) a bomb, but will actually improve the comfort of your home.

Christian.

[Dan Gravell]

Silly question now perhaps, but do all boilers support these things? I've started an email enquiry with Honeywell about their products, but I'm not sure whether my boiler will allow a programmable thermostat to be fitted. One would hope the interface to the boiler is a generic one through standard inputs.

The boiler is no more than ten years old, I think.

Dan

[Christian McArdle]

Every gas boiler ever made that uses electricity can support a programmable thermostat. They will have one of three methods:

1. "Voltage free" contacts (just connect the thermostat terminals across the boiler thermostat terminals)
2. "Call for heat" input (just connect the thermostat terminals across the call for heat input and the live.
3. Main power input (just connect the thermostat terminals between live and the boiler power input.

(3) Would be required for really ancient type boilers that just fire up when there is electrical power. Think old cast iron lumps.

Most modern boilers use method (2), as it allows most flexibility in wiring, although some (particularly combis) use method (1).

Christian.

[Dan Gravell]

Sounds good. Many thanks for your continued advice!

Dan

[chris French]

I've been using a programmable thermostat with my combi since it was installed, works fine.

Re the problem with the timer. I had an integral (electronic not mechanical) timer on mine . I used to leave I just set on all the time with control via the programmable stat. Then earlier this year it developed a fault and the timer would turn off, turning off the heating. Since i never used it, I wasn't bothered about repairing it, so I just remade the connections so that the supply to the boiler was then always on.

[Dan Gravell]

Thanks to all that have helped. I think I'm going to go the programmable thermostat way, rather than just buying a new timer for the boiler.

I've rung around a few plumbers and they've all said it's one/two hours work. I only want them to connect the base station to the boiler, I'll sort the thermostat myself (it'll be a wireless one). So this basically means about £100 labour, perhaps a little more, plus the part. So no different to getting the boiler fixed then.

My next question is, is this possible for me to do, or do you need to be Corgi registered? That's what Honeywell alluded to when I contacted them. I have the good old Collins book but it doesn't give decent instructions on how to fit these things, which might be telling.

Thanks again, Dan

[Christian McArdle]

It is a very simple job, not dramatically more complicated than wiring a plug. There is no need for CORGI registration. However, exactly what will be required will depend on the thermostat chosen and your boiler. Do you have model numbers?

Christian.

[Dan Gravell]

I don't know any more than the fact that it's a Sime Friendly, I believe there are a few "sub-models". I don't have a manual (any more), something I want to chase up...

Thanks, Dan

[Christian McArdle]

Can you find the electrical terminals? Are there any markings? Are two of the terminals linked together with a bent bit of wire?

Christian.

[Relict of EricP]

Yesterday, I was shown written confirmation that the electrics of a boiler are not considered to be within the Corgi remit for gas. This was by the engineer for a large domestic appliance supplier.

The engineers are trying for Corgi registration and their employer don't want to pay for them to do it.

So it seems, in their opinion, anybody can fiddle with a boilers electrics.

[Dan Gravell]

I'll have to get back to you tomorrow, as the boiler is at home and I don't have newsgroup access at home (or rather, I haven't set it up). From memory there is wire, (including a yellow/green one?) these are connected to the pipes on the boiler.

Dan

[raden]

In message , Dan Gravell writes

Absolutely not if you're competent

I came late to this thread, but it's all here in uk-diy

[raden]

In message , Relict of EricP writes

It has nothing to do with opinion

The only requirement is "competence"

[Dan Gravell]

I had a look last night. The boiler is boxed in which makes it difficult to look inside, I can take the boxing off when I need proper access but didn't have time last night.

I found where the mains goes into the boiler, is that what you mean? I was looking at some manuals for more up to date Sime boilers which contain details of all kinds of terminals in the control panel and thermostat box of tricks.

If not I need to do more digging around in the weekend.

Ta, Dan