Bottom of radiators cold

[sncooper]

I had a brand new central heating system installed last year, but am not pleased with its performance. The bottom half of my radiators are stone cold - the problem is with the downstairs radiators, upstairs ones get very hot.

There are 9 radiators on the system, 5 upstairs and 4 downstairs. I have tried balancing the system. Currently, the downstairs valves are completely open. The upstairs radiators are open about 1/8th or 1/4 of a turn.

Once the upstairs radiators reach temperature and the TRV's shutdown the downstairs ones do get a little bit warmer, but nowhere near as hot as the upstairs ones are able to get. The Radiators are Myson Select - their web site suggests that my problem is due to flow rate.

I am wondering if the problem is beacause my boiler's pump is not powerful enough or if it is because the pipe is not thick enough (it is 10mm microbore) ?

I have 1 radiators in the loft, 4 on the first floor, and 4 on the ground floor and a Vokera Linea 28 boiler. The complete system was installed brand new last year.

Is it possible to turn up the pump on a Vokera Linea 28, and if so is it something I can do, or do I need to call a plumber out (I am a qualified electrician) ?

Thanks,

 

[DP]

Get the engineer back and get him to sort the system.

Did you check his CORGI card? Do you have a completed Benchmark logbook? Do not open the boiler. The pump setting will be correct. Altering the setting will reduce pump speed and make things worst. Strongly suggest you contact the fitter as this will be circulation problem

 

[sncooper]

Thanks for the advice - I already spoken to the plumber about the problem, but he's too busy to come back and look at it for a few weeks.

He said that it is normal for the bottom half of the radiators to be cold - which I think is bull, as the old radiators used to get nice and hot.

Have you any ideas what might be causing the problem ?

 

[Bahco]

I had a brand new central heating system installed last year,

Did your plumber replace all the copper pipes too, I,m thinking it may be sludge in the system

 

[brumylad]

Balance the system.

Do this using the lock shield valves. Start with the rad nearest the pump. Turn the valve fully clockwise then back 1/4 turn. Try this for each rad opening the valves a little more as you move away from the pump. However be careful not to run the system with all the lockshield valves closed at any time as there will be no circulation and u might bust something.

Good luck

 

[kevplumb]

if the rads are cold halfway down youve got flowrate probs (morning oilman)

 

[PEDANTICVINDICTIVEMAN]

What btu output are the rads which are cold which are fed with 10mm

 

[kevplumb]

morning pedantic

 

[PEDANTICVINDICTIVEMAN]

Mornin Kev, knackered before starting this week after fitting CH in 3 days with that bloody Ideal Mini and dodgy stat making life difficult last week, getting old

 

[kevplumb]

were all getting old mate

 

[sncooper]

Hi Guys, my system is a bit better after balancing, but would like to improve further if possible - I don't have the experience you guys have built up so would appreciate any advice you can give ...

The boiler is in the bathroom, and the mainfold is pretty central in the landing. The smaller rads get very hot, and the larger ones get hot at the top and warm half way down.

I found that the radiators closest to the manifold got hot really quickly, so have turned these down to 1/8 of a turn, with the bedroom radiators at 1/4 of a turn, and downstairs are fully open.

Are the downstairs rads OK fully open, or should I turn these down to 1/2 a turn ?

I have a laser beam thermometer and have checked the temperature on the input and outputs of the radiators - upstairs give about 10C difference, but downstairs have a 20C difference.




Here are some facts and figures about my system:

Boiler = Vokera Linea 28 = 95,563 BTU output
Radiators (x 9) = Myson Select = 41,637 BTU output

Complete system is new, including all piping, TRV's and Radiators.

Downstairs radiators with the 'cold' problem are:
5033 BTU, 7321 BTU, 5656 BTU, 4399 BTU.

Upstairs radiators are OK:
3289 BTU, 5491 BTU, 3142 BTU, 5948 BTU.


Should I expect an even distribution of heat on the top and bottom of each radiator, or are they always going to be hotter at the top than the bottom ?

Thanks

 

[brumylad]

the total heat output of your downstairs rads alone is over 22, 000 BTU.

If the downstairs rads are run off a downstairs manifold, using my rule of thumb (yes I know I'm lazy) I would have run up to the manifold supplying these in 22mm pipe.

If the downstairs is supplied off the same manifold as the upstairs then the resistance of the micro-bore will be pretty high and certainly the pump will have to work pretty hard.

What is the diameter of the pipes going into the manifold(s). ?

In my experience the top of a radiator is always hoter than the bottom, but the bottom should still feel hot.

Try turning the lockshields on the upstairs rads a little more. I think the temp drop most systems aim for is 11 oC

 

[kevplumb]

9 deg across the rad
11 deg across the boiler
if you have big rads 10mm aint going to cut it your installer should have known that

 

[sncooper]

The main feeds in/out of the boiler are 22mm and have two mainfolds connected in series - both mainfolds are under the landing floor. I presume that one is for the upstairs rads and the other for downstairs.

All pipes are 10mm plastic.

I live in a Victorian house with high ceilings, so it tends to need a lot of heat to get it warm. There is no one living next door at the moment so no heat coming from that side - the temperature of the walls in the hall is 12C compared to 21C on the heated side - I can really feel a draught coming down the stairs.

I also find that the Kitchen is only 18C compared to the rest of the rooms which are about 24C.

Is the concensus that I should have downstairs re-plummed with 15mm pipe ? Is this likely to cause any problems to the upstairs rads that are on 10mm ?

 

[kevplumb]

why are the manifolds in series
could be the problem