Hints/Tips part microbore system

[Riley]

Morning all

i fitted a new boiler last week and customer is complaining of no heating downstairs. Upstairs in 15 mm downstairs microbore.

I was thinking just a balancing issue. But have shut of all upstairs rads to force heat down stairs and no change. There is water at each flow and return downstairs so no blockage but as soon as rad is reconnected heat does not transfer to the rad.

any thoughts with this??

many thanks

 

[gassafe]

Did the system heat up okay on the old boiler? Did it even heat up last week when you tested it? Is this tank fed or a combi type system?

 

[Riley]

Sorry mate more info needed. Yes system did used to heat up and was hot when I left after boiler changeover. Boiler is now a combi going from a vented system. Owner is most definitely a fiddler and would have no doubt come straight in and adjusted the trvs. I have put them back to where they were (not that it should make much of a difference) as all lockshields are fully open downstairs.

 

[gassafe]

Does sound odd, I would have thought shutting the upstairs 15mm circuit would have blasted it round downstairs...

Is it a very old system, possible 1 pipe or did you swop the flow & return & maybe an old check valve hidden somewhere?

 

[Riley]

Vaillant 837 installed 5 bed house. I know!!! Would've fitted unvented given the chance. Customer was adamant that's what they wanted.

 

[Riley]

I guess check valve is a possibility. As far as I'm aware I have stuck with the same pipe layout. Ie same flow and return. And I have had the system hot so I'm guessing nothing has changed. As I say I can get hot water to each rad downstairs so am again assuming that there is no real issue with the piping. I have just realised that I missed one trv upstairs that wasn't bi-directional but have now changed that but still no difference

 

[Riley]

House is under 20 years old. Sorry should've said that

 

[Riley]

I fecking hate microbore!!!!!!!!!!

 

[Best]

Have you tried taking whatever is the easiest rad off downstairs and opening each valve into a hose for several minutes while the filling loop is opened to replenish the pressure?
Micro bore is terrible for air locking. I hate it also

 

[Riley]

Thanks best I will give it a go . As I think I said above though I have opened each downstairs radiator valve into a bucket And each will run hot but as soon as I reattach the radiator they go back to cold

 

[dancinplumba]

Maybe the return is blocked ?

 

[on31ll]

How dirty is it ? Pump on boiler ok ? Any external pump still on system ?

 

[on31ll]

How dirty is the system i ment to say

 

[Riley]

Thanks all for coming bacK. System is very clean Was actually quite proud of how clean I got it. It is a CombI installation and pump is working exactly as it should. I should point out that the boiler is in the loft

 

[Riley]

Also brand-new radiators throughout

 

[on31ll]

No pump left on from when it was vented ? No valves left on ?

 

[Riley]

No ripped it all out myself mate. It's most confusing. I could almost understand it if there was no water at the rad valves but there is, it's warm and when you add a rad it stops again

 

[on31ll]

All the rads upstaires definatly shutting off ? No bypass ?

 

[Riley]

No bypass. I am going to have to have some more floorboards up I think Damn

 

[on31ll]

Yer mate think your going to have to lift more boards. Once the rad upstaires are shut off does the boiler keep running ? Because it must be heating somthing somwhere.

 

[Riley]

I think its short cycling somewhere mate as it goes on and off nearly constantly. Back there later fingers crossed

 

[tolly]

I think its short cycling somewhere mate as it goes on and off nearly constantly. Back there later fingers crossed

I would try turning all upstairs rads off, then fire CH, see if you get any heat on return by boiler.

 

[Riley]

Cheers Tolly, all upstairs rads are off and nothing boiler is now short cycling getting to temp and overrunning

 

[on31ll]

So the return is blocked ?

 

[tolly]

Cheers Tolly, all upstairs rads are off and nothing boiler is now short cycling getting to temp and overrunning

When you say nothing I assume you mean your getting no heat on the return with just microbore rads on so it cycles.

Does sound like return is blocked