Rads slow to heat up after new boiler install

[shambolic]

Is the hot water cylinder piped in 22mm if it is I would fit a valve on the return and close it down to force heat to rads more when first turned on.

 

[DazzarGaz]

when the ch and dhw are turned off, is the boiler completely dead. I.e. No lights at all including the big blue one?

 

[DazzarGaz]

when the ch and dhw are turned off, is the boiler completely dead. I.e. No lights at all including the big blue one?

 

[nhg66]

when the ch and dhw are turned off, is the boiler completely dead. I.e. No lights at all including the big blue one?

The blue light is always on even when the programmer has the heating set to off.

 

[nhg66]

Is the hot water cylinder piped in 22mm if it is I would fit a valve on the return and close it down to force heat to rads more when first turned on.

All the pipework in the airing cupboard is 22mm. The CH main feed drops into the kitchen behind some fitted units and it appears that there is a 15mm spur coming off that as this is where the downstairs rads are connected and where the new 10mm plastic pipes connect. I cannot see whats going on behind the cupboards without ripping the kitchen units apart.

 

[nhg66]

As a test, if I switch everything off and start from a cold system but with the HW up to temp via immersion, how long would you say it SHOULD take for the rads to heat up to normal operating temp ?

 

[tonybhoy]

As a test, if I switch everything off and start from a cold system but with the HW up to temp via immersion, how long would you say it SHOULD take for the rads to heat up to normal operating temp ?

Hard to say without seeing your system and the size of your house but generally speaking about 20 to 30mins.

On a fully pumped system the hot water cylinder with an older type of coil the recovery time should be about 30mins.

 

[nhg66]

Guys, cheers for all the help thus far

Right, I have tested as follows :- Hot water off, system started from cold with max heating demand, all rads open fully.

After about 2 mins, the 22mm Hot feed pipe by the pump starts to warm up, boiler output 45C and rising, hot water flowing past 3 position valve into the main CH 22mm pipe, rads starting to get warm by the inlet TRV's.
5 minutes in, boiler running at steady 66 degrees (set at 4-5 on the boiler dial) most rads warming nicely except the 4 downstairs that have been repiped from 8mm microbore with dual entry rad valves to 10mm plastic with TRV's. These 4 rads are heating up much more slowly and the metal part of the lockshields is cold suggesting that flow is minimal because the other rads in the house have hot lockshields by now.

So, I lift some floorboards to check the pipe run and also remove a piece of fascia in the kitchen where the main 22mm feed drops down to ascertain how they are connected. What I find is that the 22mm feed drops down to 15mm and passes through the wall from the kitchen to the dining room where I have lifted the floorboards. Prior to the repiping, this 15mm pipe ran all the way through the underfloor void to the lounge with the 4 rads tee'd off along its length, each of the 4 rads running 8mm to the rads.

What I have now is all 4 10mm pipes terminating at the piece of 15mm that has stepped down from the main 22mm feed. Is this a bottleneck ?

Also, the 22mm feed coming down behind the fascia I removed is as hot as the pipe by the pump (boiler output temp ish) but the 22mm return back from those 4 rads is significantly colder.

So, because the upstairs rads are getting hot and only the 4 that have been repiped downstairs do not, is it fair to say that its unlikely to be the pump and more likely to be the way those 4 have been piped and the diameter of said piping

 

[tonybhoy]

Try turning off the upstairs rads and see what happens to the downstairs ones. Does sound as though these rads have been piped wrongly but I would still replace the pump regardless.

 

[nhg66]

Tony,

did as suggested, all rads off except the four problem rads. They heated up more quickly and the heat was starting to permeate down to the bottom within 20 mins with the return pipe getting warm.

 

[tonybhoy]

Tony,

did as suggested, all rads off except the four problem rads. They heated up more quickly and the heat was starting to permeate down to the bottom within 20 mins with the return pipe getting warm.

First thing to do is change the pump then I would be looking at the pipework to those rads.

 

[Statia]

Have you tried opening up the lockshield valves up a couple of turns on the 4 colder rads, one at a time, and see if they get hotter? You should notice a difference quite quickly if the water in the system is up to a nice temp already.

Costs nowt and might do the biz!

Friday afternoon jobs are always "let's go to the pub" jobs, so if in doubt, get the fitters back in and let them sus out the problem. They should have left you with a fully working system.