Twin entry radiator valves, fitting new combi boiler, help!

[Chrishome49]

Hi there,
I have an old vented central heating system with baxi boiler in the kitchen and hot water cylinder in the loft. Old boiler barely working so getting quotes to replace with a combi and remove cylinder etc.
11 radiators in the house, 6 of them have twin entry valves with both pipes feeding into the one valve. Do these twin entry valves need removed and replaced with single entry valves due the the pressure of the new combi? I've been told yes, and no but very confused.
Thanks.

 

[ianmcd]

yes they will need replaced, the most common way is to connect to the old return at the opposite end and run the new pipe behind the rad unless its easy to run the new pipe under the floor, to be honest if it was my house I would fit new rads at the same time thay are not that expensive to buy the expense is in having the system drained and re-filled, if you do it all at the same time it is much more cost effective

 

[leakydave]

Building regs require the fitting of TRVs at the very least in the bedrooms... but I would do the whole house, other than bathroom and room with wall stat.

 

[Chrishome49]

That's great info thanks, I'll run it past the engineer tomorrow. If anyone is able for a 'homer' combi boiler replacement job in Stirling, let me know. Apparently current 15mm gas pipe not sufficient, and need a new run of 22mm, but I having it fitted externally on outside wall.

 

[Agile]

You do not HAVE to fit TRVs if you really dont want to. Although its always advisable. Better to to get rid of the microbore if possible!

But why have a combi?

I would always recommend a new heat only boiler which is cheaper and keep the ( or a ) cylinder. They give far better performance than a combi!

Tony

 

[Chrishome49]

What is microbore? Does that describe the twin valve?
The house is quite a big old draughty place and hall thermostat turns the whole system on or off so will prob stick to that rather than trvs. Have just been told the twin valves could burst under pressure of new combi.

Current 9kw electric shower also failing, with failing old baxi boiler. Needing a combi to plumb in new mixer shower and current cylinder only half fills the bath. 3 of us in the house so can't keep risking running out of it water.

Thanks.

 

[ianmcd]

Microbore just means 8mm pipe and the valves wont Burst but they will almost certainly leak, for the sake of a price difference of about £10 max I would install TRVs but as advised you dont have to

 

[Agile]

All the twin entry valves that I have seen are designed for 8 mm or 10 mm bendible pipe.

10 mm worrks OK but 8 mm gets blocked so easily and has a problem getting enough flow in most cases.

Tony

 

[ianmcd]

just for clarification OP micro bore is 8mm and mini bore is 10mm they were both very popular at one time and 10mm is popular again with installers in the PE version but neither is used much these days in the copper version for radiators, doesnt mean that it wont still work though, the twin entry valves that you have are bad news I would definately get rid of them