cold radiators second floor

[myson]

Have just extended my heating system to 2nd floor attic (2 rads + towel rail). Can only get all 3 hot if downstairs rads switched off and 1 hot at best with rest of house on.Have balanced all rads to give priority to attic. Boiler in bathroom on 1st floor - pump Myson Compact - under bathroom floor is on full speed (setting 3). Total rads including attic - 11.
Any ideas?

 

[Bahco]

How have you piped these rads?

Are they fed off the 22mm flow and return?

 

[myson]

Yes, they are fed off the 22mm flow and return immediately after the 1st rad on the system using 15mm plastic.

 

[bengasman]

How old is your pump, are you sure it is still giving full spec?

 

[Bahco]

Is the F and E tank above the rads?

You can always look through the points in the FAQs post no 8.

 

[myson]

How old is your pump, are you sure it is still giving full spec?

Pump is quite old but didn't want to change it without checking if might be something else first.

 

[myson]

Is the F and E tank above the rads?

You can always look through the points in the FAQs post no 8.

Yes, the base of the tanks are about 3ft above top of rads.

 

[myson]

Is the F and E tank above the rads?

You can always look through the points in the FAQs post no 8.

I know this sounds silly but as a new member today where are the faq's & post 8 in particular?

 

[myson]

Is the F and E tank above the rads?

You can always look through the points in the FAQs post no 8.

Yes, the base of the tanks are about 3ft above top of rads.

Sorry Bahco, just seen faqs at top!

 

[myson]

Is the F and E tank above the rads?

You can always look through the points in the FAQs post no 8.

Yes, the base of the tanks are about 3ft above top of rads.

Sorry Bahco, just seen faqs at top!

I have checked all the things suggested on the faq 8 without success. the fact I can get them hot in isolation suggests no blockage/air etc.

Could it be piping should be 22mm not 15mm (other 2 floors are 15mm after initial 22mm feed/return from boiler)?

I have been thinking it's the pump which although it works for original circuit may be struggling even on speed 3 (leaflet says 1900rpm, 112watts input, 0.47amps) with extra uphill battle?

 

[bengasman]

No sludge in open vent is highly unlikely, it may not be completely clogged up, but there will be a lot more than I would care to have in my dinner.
Chuck a bottle of cleaner in, my preferred is “hyperflush” from kemco, and leave that running for a couple of weeks.
If your pump is old, changing that for a nice new grundfoss wouldn’t hurt either.

 

[myson]

No sludge in open vent is highly unlikely, it may not be completely clogged up, but there will be a lot more than I would care to have in my dinner.
Chuck a bottle of cleaner in, my preferred is “hyperflush” from kemco, and leave that running for a couple of weeks.
If your pump is old, changing that for a nice new grundfoss wouldn’t hurt either.

Given the foregoing what pump size etc would you suggest - there appear to be several different types/sizes at B&Q.

 

[bengasman]

grundfos 15-50 should be ample

 

[myson]

grundfos 15-50 should be ample

Thanks, Bengasman, will give it a go.

 

[welsford46]

Post deleted