CH yes HW no - absolutely stumped

[kroma]

Have a Potterton Nrtaheat MK2F 10-16 with a pumped CH and gravity HW by indirect heating via cylinder. recently had bathroon brassware replaced and ensuite replaced with new shower unit and sink. At this time rads in both locations were replaced by heated towel rails. before all this occured everything was fine.

All radds and towl rails are fine, but no HW. there is no circulation throigh cylinder. No air in system for sure, cylinder feed gets hot bu cylinder return to boiler does not warm up. feed and return pipes cut, circulation pump fitted to clean return - boiler-feed loop and also cylinder ip to cylinder op. . feed vent is clear and well clear of water level in the overflow tank in loft. What can it be?? maybe the cylinder coil is blocked too much for gravity feed to circulate? Cleaning agent was added to HW and left for 3 days before we tried the circulation pump.

Any ideas??

 

[ArtfulBodger]

Sounds like you do have air in your system on the gravity HW side.

 

[kroma]

Sounds like you do have air in your system on the gravity HW side.

Gravity return pipe is not that long, it has been replaced in part due to this issue, the CW feed pipe was moved to be at the bend to the vertical where the pipe goes through the floor directly to the boiler. have had a plumber doing this for 2 weeks now - he never seen anything like it!

 

[kevplumb]

you HAVE AIR IN SYSTEM

 

[kroma]

you HAVE AIR IN SYSTEM

Its a short run (1.75mtr) from the cylinder return to the boiler and I can not work out how to purge air in this section, the plumber who was looking at it did not reckon thta boiling the system would help, but if it must be air would this help?

 

[kevplumb]

wont do any harm

 

[kroma]

wont do any harm

: I will bleed the upstairs radiators using a sponge and bucket despite there only being water when i initially open the bleed plug, and then boil the system if no success. Am very gratefull for all respondents help, guess the Cylinder must be ok.

Tks

 

[ArtfulBodger]

wont do any harm

: I will bleed the upstairs radiators using a sponge and bucket despite there only being water when i initially open the bleed plug, and then boil the system if no success. Am very gratefull for all respondents help, guess the Cylinder must be ok.

Tks

Huh? tell us more!

 

[kroma]

wont do any harm

: I will bleed the upstairs radiators using a sponge and bucket despite there only being water when i initially open the bleed plug, and then boil the system if no success. Am very gratefull for all respondents help, guess the Cylinder must be ok.

Tks

Huh? tell us more!

I will try to explain myself, I just can not think of any way left to purge the system of air, all else has been done other than boil the system. Bleeding the RADs has only resulted in a little air coming out in the past. All my rads are evenly heated. So I summise that the sole solution is to just bleed a rad or two on the upstairs circuit and let quite a lot of water out and just maybe, maybe this will work.. We even forced mains pressure down the feed pipe to the return....i am just out of ideas...It surely cant be a restricted Cylinder coil pipe..can it?

rgds

 

[wilhelm]

all i can think of is to drain down again, disconnect the coil upper/lower pipes, and blow through to see if there is restriction?
lets us know how you get on,