Radiators not heating , poor circulation?

[Olivias Grumpy]

Hugh
All 3 removed are at the end of system. I have left wide open and closed a few close to boiler. This does allow the 3 rads to obtain some heat but not enough.
Checked operation of TRV all ok

Cheers

 

[Hugh Jaleak]

Close all but one. See what happens. If this heats up, close it, and open another, before closing first again. If there is an air lock, putting all the pump's effort into one rad may push it through.

 

[hossacd]

Have you checked the temperature of the return pipe to the boiler when the radiators aren't heating up ? If the flow and return are similar temperatures the water is finding an easier path back to the boiler.

I had a similar issue with the furthest away radiators not heating up well even with the hot ones being turned off. I traced it back to a faulty/miss-set bypass valve which was fitted a fair distance from the boiler, it was a manual valve and we had just moved in unsure if it was set wrong on install or started passing more over the 20 odd years since the system was fitted. I simply closed it as the system has several radiators with no TRVs and it resolved the issue and also caused significantly less cycling of the old fixed output boiler.

 

[Hugh Jaleak]

Any possibility a pipe has been crushed somewhere, thus impeding the flow?

 

[Olivias Grumpy]

Hi Hugh
No evidence of any damage to pipes anywhere

Hello hossacd
I have been thinking on similar lines, that flow is getting back to easily
Going back to St Albans (sons house) on Sunday for Xmas
I intend to fit an auto bypass valve on Wednesday

Regards

 

[Olivias Grumpy]

Good Morning
Update to those who have been interested and to anyone who can help further.

On Wednesday I drained system after cleaner had been in for 9 days, fluid still quite clear.
Then removed the original bypass gate valve. It was found to be seized at more than 1/2 open. Fitted an Auto Bypass Valve in same place.
Left setting at default position about 0.2 bar.
Filled and bled system plus added inhibitor.
The heating circulation improved a lot, I managed eventually to get heat from all rads in system by balancing? And adding 1 rad at a time.
It is now the best it has been this winter , however I don’t think I’m quite ther yet.
Could anyone advise the best setting for the bypass valve? I’m sure ther must be a way to calculate it?

I’ve also now noted that the boiler stat is set st 4-5. If I turn it up to MAX it runs correctly for a short while and then trips on Overheat Stat and requires resetting underneath boiler.

So I’m thinking boiler is getting too hot from recirculated water via bypass, am I correct in my thinking?
Would increasing the pressure setting on the bypass valve help in any way?

Thanks for reading

Cheers

 

[D_Hailsham]

Could anyone advise the best setting for the bypass valve? I’m sure ther must be a way to calculate it?

I’ve also now noted that the boiler stat is set st 4-5. If I turn it up to MAX it runs correctly for a short while and then trips on Overheat Stat and requires resetting underneath boiler.

So I’m thinking boiler is getting too hot from recirculated water via bypass, am I correct in my thinking?
Would increasing the pressure setting on the bypass valve help in any way?

Your thinking is correct.

Do you have two zone valves or one mid-position valve? This affect the setting of the bypass. (Which bypass have you fitted?)

A thermostat setting of 4 to 5 is about 71C to 77C. You shouldn't need it any higher for central heating, but it can't be much lower or the hot water cylinder will not get hot enough.

 

[Olivias Grumpy]

Hi
2 Honeywell zone valves are installed
I fitted a valve from Screwfix
Not sure of make. I’ll find out

 

[Olivias Grumpy]

Rob Pond Heating Solutions
Is name on valve paperwork

 

[D_Hailsham]

Rob Pond Heating Solutions
Is name on valve paperwork

Rob Pond do not make the valve; they have it badged for them.

I see there is an Alpha 2L pump. Which setting is it on (I,II,III,PP1,PP2,CP1,CP2)?

 

[Olivias Grumpy]

Thanks for Rob Pond info. That explains why they weren’t very helpful with any pointers re setup.

Pump is currently set to PP2 which is factory set , and recommended for 2 pipe heating system

 

[ChrisNason]

Made by Intatec...
http://www.intatec.co.uk/products/automatic-by-pass-valves
For instructions

 

[Terry lambert]

A good description here on how to set up an auto bypass

https://www.pegleryorkshire.co.uk/M...003/89827351_Terrier_By-pass_valve_678021.pdf

 

[Olivias Grumpy]

Thanks terry
I’ll start having a read and findinding boiler flow etc

Cheers

Hello Chris
Thanks for info
Cheers

 

[D_Hailsham]

Pump is currently set to PP2 which is factory set , and recommended for 2 pipe heating system

You can't use a PP setting if you have an ABV. This is because the ABV will open more as the pump pressure increases. So mmore water will be diverted straight back to the boiler. You can either run on a fixed speed (I,II, OR III), or you can fit a manual valve after the ABV, which limits the flow through the bypass circuit and allows use of a PP setting.