New Radiator slow to get hot

[vessy]

I'll try to explain as best I can!

Newish build house (1994) has 10mm microbore heating pipework, gravity fed CH system.

We have just converted out garage into a day room and added a radiator, I decided to tap this into the radiator feed from the bedroom above, firstly because it was a much easier route but mainly because all the upstairs radiators are small (500x500) where as downstairs rads are large (1200x600) and some doubles. I know that there are separate manifolds for upstairs and downstairs so figured the downstairs already had a large load, plus the house isn't the warmest so didn't want to hinder any existing downstairs rad, remembering it's all microbore.

Problem is the new rad (1200x500 double) doesn't get very warm, all the other rads are hot to the bottom after about 10 mins but this one is only hot 1/3 of the way down. Strangely the rad it is connected in parallel with still gets just as hot as before, just as quick!! all this is with the new rad valves fully open.

So far i have done the following;

Shut off all upstairs rads, new rad got hotter a little quicker but still not anywhere as hot as the downstairs.

Removed the new rad and opened both valves into a bowl, got similar good flow from both.

Checked all now pipework for kinks and no problems found (didn't expect any as flow above was good) new rad is in parallel with existing rad so definitely connected to flow and return.

The only thing i am worried about is the 10mm microbore (plastic) has been connected using inserts to help them seal, these have an internal diameter of just over 5mm, but why would i get good flow with the rad removed?

Do microbore systems have some kind of flow restrictor in the upstairs manifold?

Really confused with this one, any help or advice would be priceless.

 

[sime10]

What was the size of pipe you tapped into?

 

[shaunyab]

have yoy tried shutting off all the rads except the new one?

 

[vessy]

The whole house is 10mm, so i just went like for like, only thing is it's 10mm copper, i have put in 10mm plastic with these seal inserts that have 5mm internal diameter!! Just can't work out why they would restrict pump flow and not gravity pressure flow with valves open to air.

Haven't shut off all rads only upstairs ones, will try that now.

 

[sime10]

So you connected 10mm pushfit to 10mm copper with a tee is that right?

 

[vessy]

Exactly, the pipe run has one inline half way along (had to do this whilst builders built studwork to cap off and keep house heating working) and then connected to the rad valves, each run has 4 of these seal inserts in place.

 

[sime10]

Not sure If I have got this right but you have teed into an exsisting feed of 10mm to another rad?

 

[vessy]

Yes, the rad i tee'd into is very small (500x500 single) the valve is backed right off, about 1/8th of a turn open following a balance last year, this rad gets hot at the same rate as all other rads, i would have thought there was plenty of enough excess flow to this rad.

Just turned every rad off in house bar the new one and one of similar size on downstairs circuit, the new rad got hot much quicker, but other rad still got hot quicker!!

As i said earlier the existing rad I tee's into has not suffered any loss with the new rad connected and fully open.

 

[sime10]

You may be starving the new rad of hot water, It is bad practice to take 2 rads off 10mm pipe.
Also it could be the positioning of the tees to the flow of water.
But I would say taking 2 rads off 10mm is not a very good thing to do.

I would have gone back to the 22mm pipe

I have seen this problem many times before.

 

[shaunyab]

Did the problem rad get alot warmer all over? if so then it may be a case of re balancing.

 

[sime10]

shaunyab are you reading as well as answering?

 

[shaunyab]

yep, but not beating around the bush

 

[sime10]

yep, but not beating around the bush

What bush?

The pipes have been teed into 10mm to feed another rad bad practice no bush

 

[shaunyab]

i totally agree with you, but to try to get over the problem without re plumbing, maybe re balancing might help as you quite rightly have pointed out the rads flow through it is being restricted so it may help.

 

[vessy]

OK so i guess this is a lesson learnt, my only curve ball is why when the existing rad i tee's into is turned off do i still have this problem? pipes have been tee's about 12" back from existing rad.

If it were a balancing issue with the new rad fully open shouldn't this be taking the flow, thus affecting all the old rads that are backed off from previous balance?