Advice re: Adding a radiator to CH System

[Terry Paterson]

Hi There,

I live in what is a converted bungalow, and the two rooms upstairs have no radiators, although there are five downstairs.

I think the boiler isn't a combi-boiler ? (Gloworm Hideaway 50B), as it does'nt heat the tap water as required / immediately ?

instead there are feed? and return? pipes on one side of the boiler which go upstairs and supply an indirect? hot water cylinder in a cupboard,

and on the other side of the boiler are another pair of pipes which seem to be the feed? and return? for the radiators.

the header tank for the system is in the remaining attic space above one of the bedrooms.

-- so -- should I be able to simply run a couple of lengths of pipe from the system downstairs to the bedrooms upstairs ?

I'm guessing since the boiler is already sending/pumping water upstairs to the hotwater cylinder, I should also have enough pressure to supply a radiator or two upstairs also ? (I can't see any obvious pump on the boiler -- at least not like the ones I've seen elsewhere

-- electrically driven, round, with a plastic housing)

From what I understand -- the feed and return pipes from the boiler are sometimes called "manifold" pipes ? and for each radiator there is normally a pair of 15mm pipes coming of each manifold pipe and supplying the radiator ?

so theoretically - I should be able to cut the 22mm pipes - and add a couple of reducing T's -- to which I can connect some more 15mm pipe to be routed to the upstairs ?

I have managed to do a little bit of re-routing of pipes in the bathroom before using 22mm copper pipe, and compression fittings - so I'm willing to give adding a couple of radiators a try if the procedure is similar.

This should also give me a good opportunity to drain down the system and add some sort of corrosion inhibitor since Scottish Gas have told me that my system needs cleaning out -- but want to charge around £

500 for the job !!!

Any tips/advice gatefully received !

[Set Square]

The short answer is probably yes - but you need to understand exactly what you've got a bit better before hacking into it!

How many header tanks are there in the attic? Is there a big one for the domestic hot water and a smaller one for the primary heating circuit? Is there a bomb-like pressure vessel anywhere?

What controls are there? I presume that there's a programmer, with switches for HW and CH? Is there a room stat? Are there any motorised valves? Can you have CH without HW?

My guess, pending answers to some of these questions, is that it's a vented (as opposed to sealed) system with gravity (convection) circulation of the primary HW circuit, and pumped circulation round the radiators. If you trace the pipework which goes from the boiler to the radiators, you should find a pump somewhere - possibly hidden under floorboards.

AIUI, manifolds are only usually used on micro-bore systems - using 8mm or

10mm pipe. Otherwise, you just have main flow and return pipes in 22mm - with 15mm tee's off for each radiator. Provided the boiler has sufficient capacity, there's no reason why you can't install another couple of branches for upstairs radiators - again assuming that the header tank is high enough - but if it's above the upstairs ceiling it will be ok. But your tappings *must* be on the same side of the pump as all the other radiators - so it's fairly important to find the pump!

[Terry Paterson]

Hi There,

regarding the first two questions :-

yes -- there are two tanks in the attic space, one which seems to supply the hot water cylinder in the bedroom cupboard below, and a smaller one which seems to supply the CH system.

I'm not aware of any "pressure vessel" - although I'm not sure what one would look like other than your description of it looking "bomb like" -- but unless it's a very small bomb hidden under the floor or such like then I don't think we have one..

Controls :

Above the boiler on the wall - is a timer/controller -- with seperate settings for CH and HW, and in the livingroom theres a temperature controller/thermostat.

I'm not aware of any motorised valves, nor a pump (although I have seen them on other CH systems - so I have a rough idea what I'm looking for) -- but as you say -- it may be that the pump is under the floor or something like that.

Is it possible that there might be no pump ?

[Set Square]

Yes, it's an vented system, like I thought.

No - there won't be one. I only asked the question in case there was only one header tank - in which case it may have been an unvented system.

Yes, I'm now fairly sure that it's a gravity HW and pumped CH system. The room stat will control the pump (but only when CH is selected on the programmer). The boiler will run whenever either HW or CH is selected - and you can't have CH only because the boiler will be on and will heat the hot water regardless.

You probably haven't got any valves - but you should consider adding at least one (see below).

It is *extremely* unlikely that there is no pump. Water won't usually circulate round radiators by pure convection and, in the absence of any motorised valves, there's be no way of controlling it.

You still need to find your pump - if for no other reason that you need to know where it is if it breaks down! Where do the CH pipes go when they leave the boiler?

Under the current building regs it would not be permissible to install a system like yours because it wastes too much energy. The meet the regs, new systems have to have a boiler interlock - which turns the boiler off when CH and HW demands are satisfied. Your system doesn't do this, but allows the boiler to cycle on its own stat, keeping itself warm, when there is no need.

One thing you could consider to improve the situation is to convert it to a C-Plan system (see

) by adding a motorised valve and cylinder stat in the hot water circuit. If installed and wired correctly, this would provide a boiler interlock - and get your system at least part way towards current requirements.

Even better would be a fully pumped S-Plan system (scroll down the Honeywell document to S-Plan) but that would involve a lot more upheaval.