Adding Cylinder Thermostat to Gravity Hot Water

[roberta1000]

I've an elderly Ideal E-Type (1978) boiler with a pumped radiators and gravity hot water system. his makes the hot water rather too hot in winter when I turn the boiler thermostat up a bit to keep the house warm.

Are there any gotchas in fitting a cylinder thermostat and a zone valve to the gravity circuit?

If this is OK then I suppose I would need to wire it so that the boiler fires when either CH or Hot Water is wanted but the pump only runs on CH? That way the boiler wouldn't cycle when both Hot Water and CH are satisfied.

 

[DP]

It WOULD make sense and be fuel efficient to install a motorised valve and cylinderstat. The gravity loop should be 28mm. Fit a 28mm zone valve. The valve will have three wires (white, orange and grey) which you will use to allow independent firing of boiler for CH or HW. You will also need to remove the mechanical link that 'activates' HW channel when CH is selected on the programmer

You will be taking another step to fuel economising if you also installed a programmable room stat

 

[Deleted member 105431]

It would make sense you upgrade the whole system to fully pumped with a new boiler if you can afford it.

 

[roberta1000]

Mmmm - well I can afford a valve and cylinder-stat but I don't have the odd £3000 or so for a boiler replacement (average I was quoted recently to install a condensing replacement) .

 

[weareleeds]

Can you afford fuel bills with a boiler running at approx 55% efficiency the quicker you change it the more you will save

 

[JohnD]

when I did the sums, changing to a new boiler was not a money saving proposition

Spend £2,000 to £3,000 and save £100 a year

You would make more putting the money in a cash ISA.

If you had to borrow the money, the interest payments alone would exceed the fuel savings.

 

[roberta1000]

If you had to borrow the money, the interest payments alone would exceed the fuel savings.

Yes John I had worked through that too. And of course actual savings aren't the same as headline maximum efficiency figures. Even if gas were to double in cost it would be a marginal call. My real need here is to be able to run the boiler harder without having the hot water so hot it scalds.

 

[JohnD]

on a gravity system, you will make noticeable savings by thoroughly insulating the cylinder, and the primary flow and return pipes, which are probably under the floor.

I recently did this in my old mum's house, and the summer gas usage is about half what it was last year. (the pipes have an unusually long run)

 

[roberta1000]

That's a good point because I have a bungalow with the hot water cylinder in the loft. This means that the cylinder is surrounded by very cold air instead of the more usual 20 degree environment. I'll look at getting a second jacket for it.

 

[SirBodgeAlot]

I've got a similar system and fitted a 28mm zone valve to DHW cylinder (they are quite pricey BTW). Works OK. Also fitted a Danfoss wireless control pack at the same time which works well.

I also fitted an electric immersion heater to the cylinder which we use in the summer because -

a) The gravity circuit runs through back bedroom, so would cause unwanted heating of room.

b) It is really annoying listening to the boiler short-cycle when only DHW heat is required.

c) I'm pretty sure it works out cheaper.

d) Also save gas not having pilot light on constantly (very old Baxi Bermuda, we totally put out of service and isolate gas supply during summer)

Hope this helps

 

[D_Hailsham]

Honeywell call it a C-plan

View media item 827 View media item 73

Also see Honeywell Plans

 

[solar36]

Hi Robert,

I was wondering how you got on with the modifications to fit the zone valve and stat.

How did it work out for you.?

I am looking to do something similar.

Regards, Tony