can i fit a cylinder thermostat to my older potterton system

[rolysatch]

hi

i just had a new gas valve and pcb fitted to my potterton kingfisher mf rs70 boiler after it packed up recently. so after the expensive of that we'ew going to keep the boiler for a few more years. it's gravity hot water and pumped central heating.

my question is can i fit a hot water cylinder thermostat to my hot water cylinder to turn off the boiler when the water is hot enough or would my system not be compatible for something like this?


any advice appreciated, thanks in advance

roland

 

[JohnD]

yes you can do.

it would be best to convert it to fully pumped and add a 3-port motorised valve at the same time. You can get wiring and components diagrams from the makers such as ACL Drayton and Honeywell.

your programmer will have a different setting for gravity HW, this may well be a simple switch on the back.

you will need a bit more plumbing and wiring skill than most DIYers already have. I am a DIYer and did a similar job a few years back, and found it moderately complex, with the benefit of a lot of help on here.

 

[rolysatch]

thanks john, well knowing its doable is a start. i'll have a look into it, i'm competent at wiring, as far as plumbing i did my kitchen, bathroom and changed all the radiators but have never got involved in my heating system before. so it's possible that i can do it, i'll do a bit of research before taking the plunge.

thanks again

 

[picasso]

If you want to keep it simple have a look at the honeywell "c" plan.

http://www.honeywelluk.com/products/Systems/Wired-Sundial/Sundial-C-Plan/

 

[rolysatch]

thanks yes i would need to keep it simple. that looks fairly straight forward. can i just ask a couple of questions:

so the 28mm two port valve fits to the pipe from the cylinder back to the boiler not from the boiler to the cylinder? and does this need to be fitted at the cylinder end or the boiler end of the pipework or doesn't it matter?

also when we got the boiler fixed i got a quote to upgrade to a new condensing boiler but the price was high because it needed to be converted to a fully pumped system. if i was brave and converted the gravity fed water to pumped and used a 3 port valve as suggested, if i upgraded to a new boiler in the future would it be a simple and relatively cheap upgrade or would the new modifications i make still have to be changed?

 

[D_Hailsham]

so the 28mm two port valve fits to the pipe from the cylinder back to the boiler not from the boiler to the cylinder? and does this need to be fitted at the cylinder end or the boiler end of the pipework or doesn't it matter?

The important think is that the valve does not block the vent pipe when it is closed.

Potterton say you must have a bypass, e.g bathroom rad, on the gravity circuit before the valve.

Untitled

• D_Hailsham
• 18 Dec 2012
• 1

 

[rolysatch]

we already have a radiator in the bathroom that works off the hot water in some way, i'll investigate further to see how it's plumbed in.

 

[dcawkwell]

Wouldn't bother.
It will mean changes in the piping to fully pumped.
Given the boiler is old probably means the cylinder is old as well
so big lazy coil best for gravity than a pumped system.
Won't save you anything much anyway.

Run it a few years then pull the lot out and fit a combi.

 

[rolysatch]

after paying out to have it repaired i'm going to keep it for a few years now, it's a good boiler. i think i'll still do the cylinder stat and 2 port valve as suggeted.

as far as fitting a combi most people i've spoken to tell me to steer clear of them in a bigish house.

 

[mikely]

As an option, you can add a tank thermostat and achieve a better control than you have now without doing any plumbing - as shown below.

Gravity Interlock

• mikely
• 7 Jun 2010
• 3

With this interlock, the boiler will only fire if the tank thermostat is demanding heat or the room thermostat is demanding heat. You still need to have HW on whenever CH is required, so the programmer must still be set to gravity mode. It does not afford full control because, whenever the CH is running, the tank will continue to be heated whatever the state of the tank thermostat. However, it should prevent any boiler cycling once the tank is up to temperature.

 

[rolysatch]

that's another good opotion thanks mike

 

[Agile]

after paying out to have it repaired i'm going to keep it for a few years now, it's a good boiler. i think i'll still do the cylinder stat and 2 port valve as suggeted.

as far as fitting a combi most people i've spoken to tell me to steer clear of them in a bigish house.

A new boiler does not mean a combi !

It just means a new heat only boiler which would be typically about £1700 installed!

That would then save about 30% on your gas bill. It would probably pay for itself in 3-5 years from the gas savings!

Or as an investment give a return of perhaps 30% on the cost. Bet you are not getting that from your bank!

Tony

 

[rolysatch]

no i know what a combi is i was replying to "Run it a few years then pull the lot out and fit a combi."

as far as £1700, if i could get a new one fitted for that i would have. but my quotes range from £3000 to £4500. they're all saying that because it needs to be converted to fully pumped it's a much bigger job.

my boiler is about 78% efficient as opposed to the new condensing boilers, but i can live with that for a while if i can get a bit more control over heating the water with the help of the suggestions here.

 

[JohnD]

ask again in mid-summer when the installers are back from their yachts and looking for work.