Adding a wireless thermostat to baxi bermuda 45/4m

[lgthomas]

Hello, I have a Baxi Bermuda 45/4M back boiler and I was wondering if it would be possible to add a wireless room thermostat to this boiler. The current controls is a mechanical dial which just turns the boiler off up to twice twice a day and a switch to select heating or water and heating.

 

[doitmyself]

The current controls is a mechanical dial which just turns the boiler off up to twice twice a day and a switch to select heating or water and heating.

What do you do if you want water only, i.e. in the summer?

 

[lgthomas]

my mistake its water or water and heating

 

[doitmyself]

my mistake its water or water and heating

I thought it might be like that.

You have a "semi-pumped" system. The water is pumped round the radiators, but the HW cylinder is heated by natural circulation (hot water rises and cold water falls). You will have three or four water pipes connected to the boiler.

You say that the only control is the mechanical clock. How is the HW temperature controlled in the summer? Is there any sort of temperature control connected to the HW cylinder?

 

[lgthomas]

I have nothing connected to the hot water cylinder. The only thing I have is a thermostat on the boiler which is numbered from 1 to high which I set to no 3 during the summer

 

[doitmyself]

Fitting any sort of thermostat is going to be a problem due to the way your boiler works.

At the moment the boiler is turned on by the HW side of the mechanical timer. That's why you cannot have heating on by itself. In the summer you only need the boiler on as the cylinder is heated by "gravity" circulation. In the winter you also need the pump on to circulate the water through the rads, which happens when you set the timer to Heating and Hot Water.

It would be possible to fit a thermostat to control just the pump, but what you really need is a way of turning the boiler off when the house is up to temperature or the HW cylinder is hot enough, which can happen before the boiler stat turns the boiler off. You will need extra components to do this, but it will save on your gas bill as the boiler will only be working when the house or the HW needs heating up.

Your boiler is at least 10 years old, so it's not so efficient as a modern condensing boiler, but there's very little to go wrong and it's likely to last many more years. So updating the controls as suggested above is a sensible thing to do.

There are two ways you can update the controls: (1) convert to a "C Plan"; (2) convert to fully pumped. Option one will cost less, could be done by a competent DIYer, but would save less. Option one is the more expensive as it would need to be done by a heating engineer, but the savings would be greater. When the boiler has to be replaced the system will have to be converted to fully pumped to meed Building Regulations, so option two would be an advantage.

 

[mountainman]

Wire the thermostat to turn the pump on or off, that'll do the trick.

 

[doitmyself]

Wire the thermostat to turn the pump on or off, that'll do the trick.

But it won't turn the boiler off, which is what really saves the money.

I have thought of a third alternative, which is much cheaper as it only requires a second thermostat on the HW cylinder. The only disadvantage is that you cannot have separate CH and HW times, but you are used to that.

You would need a Honeywell DT92E Wireless room stat and an Honeywell L641A cylinder thermostat.

Tell me which timer you have and I can supply a wiring diagram if you want to go down this route.

 

[mountainman]

But it won't turn the boiler off, which is what really saves the money.

I have thought of a third alternative, which is much cheaper as it only requires a second thermostat on the HW cylinder. The only disadvantage is that you cannot have separate CH and HW times, but you are used to that.

You would need a Honeywell DT92E Wireless room stat and an Honeywell L641A cylinder thermostat.

Tell me which timer you have and I can supply a wiring diagram if you want to go down this route.

Why over complicate it, the OP asked a simple question and a simple answer is all that's needed imo.

 

[lgthomas]

Thanks for the replies. I am not planning on doing the work myself I just wanted to know if it was possible before I got some quotes done. Do you know approximately how much the work will cost just to give me an idea if a quote I receive is reasonable or not. Thanks again.

 

[GasmanxxxR1]

If your system is that old and so inefficient, have you considered replacing the lot, see it as an investment

 

[mountainman]

We tend not to discuss pricing on this forum.
I would personally charge two hours labour plus the cost of the 'stat.

 

[lgthomas]

Having just checked the programmer that I have is a switchmaster sm400. I do not really want to change the system at the moment as I don't spend to much on gas just under £ 500 per year, had a quote done for a new central heating system back last year and got quoted £ 2,500 - £ 3,000 form local installers to £ 6,000 from British Gas! The current system runs good not had any problems for the 7 years I have been in the property although I could do with a power flush this year. What I really want to do is just control the temp in my living room. when I have the heating on in the winter its just so hot in the living room I really could do with keeping it at a set level

 

[stevetheplumber]

might be an idea to have trvs put on the rads as well as the stat on the pump

 

[doitmyself]

Why over complicate it, the OP asked a simple question and a simple answer is all that's needed imo.

But it's not so simple as just fitting a stat to control the pump; you have to control the boiler as well. If you don't, the water in the cylinder could easily rise to 80C, i.e the flow temp of the boiler, which would be very dangerous.

 

[mountainman]

But it's not so simple as just fitting a stat to control the pump; you have to control the boiler as well. If you don't, the water in the cylinder could easily rise to 80C, i.e the flow temp of the boiler, which would be very dangerous.

This method of controlling the ch system worked perfectly well for decades, long before the invention of C, S and Y plan systems.

 

[doitmyself]

This method of controlling the ch system worked perfectly well for decades, long before the invention of C, S and Y plan systems.

I wasn't thinking of anything as complicated as one of the Plans; just a cylinder stat as well as the room stat.

 

[mountainman]

Wiring diagram looks sound, the only drawback would be that the hot water would have to be satisfied before the rads would come on.
Ok on early morning fire but less desirable when someone has a bath or shower and the rads turn off.

 

[doitmyself]

Wiring diagram looks sound, the only drawback would be that the hot water would have to be satisfied before the rads would come on.

Look at the diagram again!

If HW and CH are both on the boiler is fed from the cylinder stat, and the pump from CH ON via the room stat CALL terminal.
When HW is satisfied the HW stat switches over to SAT, so the boiler is now fed from the room stat CALL terminal.

Don't forget that both CH ON and HW ON can supply power.

 

[Reg Man]

Bite the bullet. Fully pumped system with Y Plan or S Plan then you can wire your stat through the motor valve controls with interlock back to the boiler.