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Ash · Joined: 25 Feb 2008 Posts: 11 Location: Hull

As part of recent flood damage repairs, 2 new radiators were fitted on ground floor along with new 10mm pipe. I believe original pipe was 15mm. It is 15mm on the 3 upstairs radiators. Unfortunately also recently had new boiler (OPTIA HE) fitted as old one (APPOLLO MYSON 30si) gave up the ghost. Also had new diverter valve fitted. The system was flushed out when the new boiler was fitted.

When central heating comes on the 3 radiators upstairs are red hot in a couple of minutes but the 2 radiators downstairs take 45 - 60 mins to get fully hot and even then they are not as hot as those upstairs. They are pretty hot at the top but not very hot at the bottom. The inlet pipe does get hot within a couple of minutes of the system coming on but the water does not appear to be able to flow into the radiators. Eventually it does but it takes 45 - 60 minutes.

Also when 2 downstairs radiators are 'fully' on and hot water is run for a bath or shower the 2 downstairs radiators lose virtually all heat (as if they have been turned off) and then take another 45 - 60 minutes to get back up to full heat again. Radiators upstairs stay red hot.

I would be grateful for any suggestions.

Yellowman · Joined: 03 Jan 2008 Posts: 79 Location: Sussex

If a system has been piped in a certain pipe size its not normally a good idea to downgrade pipe size really.

However all is not lost. It sounds to me like it can be solved by blancing the system.

On your radiators you should have 2 valves. A TRV on one side with numbers on and a Lockshield valve on the other side remove the caps (they should just pull off to reveal the head of the valve. Turn all your TRV valves uo to maximum. Now on the 3 rads upstairs with the 15mm pipe work turn the lockshield valves halfway down (you can count the number of turns between fully open and fully closed to determine a halfway point) Now downstairs fully open the lockshield valves.

Try firing up the system now. Water will alway take its easiest route and rather than flow round small bore 10mm pipework its main flow is in the upstairs rads with the bigger bore pipework.

If they are still taking a long time to warm up you can try closing the upstairs lockshield valve half a turn at a time to try and improve the problem whilkst making sure they have still got enough heat pumping through.

Im sure Scruff will be along later who is alot more clued up than me so he may choose to add or correct what i've said.

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

Looks good to me.

I would turn all the upstairs on off and open them one turn, then tweek them as required so all the rads are the same temp.

Ash · Joined: 25 Feb 2008 Posts: 11 Location: Hull

Thanks for the advice.

It's been suggested that a faulty or incorrectly wired diverter could be the reason why the 2 downstairs radiators lose heat when the hot water is run for a shower/bath. Is this a possiblity or is more likely to be a result of flow problems due to the narrow guage pipe?

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

Cannot find any information on the Optia, is that the new Ideal combi boiler.

All combi's cut of the heating when thee hot water is run, if you have little heat in the rads then they will go cold depending on the length of time it takes to run a bath.

Ash · Joined: 25 Feb 2008 Posts: 11 Location: Hull

The boiler is an Ideal Optia HE. It is not a combi boiler.

Thanks.

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

Thanks.

Can you tell me what controls the primary flow/return from the cylinder then, is it an 3port motorized valve.

Strange I can find no information as yet on the boiler.

Ash · Joined: 25 Feb 2008 Posts: 11 Location: Hull

It's a Honeywell Diverter. I'm afraid I haven't got the exact details to hand. This was fitted at the same time as the new Boiler.

Thanks.

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

Ash · Joined: 25 Feb 2008 Posts: 11 Location: Hull

It is definitely a diverter. I will be able to supply the model details tomorrow.

Thanks.

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

Ash · Joined: 25 Feb 2008 Posts: 11 Location: Hull

The diverter is a Honeywell V4073A and the boiler an Optia HE 15 cast iron wall hung boiler. I'm afraid I can't supply diagram of connections. I'm relying on the plumber to get that right. I don't know what he did.

Thanks.

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

Thats a mid position valve.

I can only think it's connected wrong, the rads you could balance and see what happens, but I would get the guy back, unless you can do a sketch for us

Ash · Joined: 25 Feb 2008 Posts: 11 Location: Hull

I will get the plumber back as you suggest. One thing that puzzles me is if the diverter is connected incorrectly why would it be that only the 2 downstairs radiators lose heat when the hot water is run whereas the 3 upstairs radiators stay red hot. I am concerned that the narrow guage pipework downstairs is the cause of the problem.

Thanks for your help.

thescruff · Moderator Joined: 03 May 2003 Posts: 4659 Location: Bath

I think the answer is with how the 2 new rads are connected, at the moment I can't think of a good reason why they should go cold when you run the hot water, unless they have been connected to the wrong pipes.

You could try balancing them as above and see what happens.

Not sure about the diverter, I could really do with a pic or sketch.