Jaguar Boiler

[Leakypipes]

Hi, I've just had a boiler moved by my mate (an approved gas engineer) - who's now on holiday!!! - (old Plumbcentre - Jaguar - I know they don't have good press but its been fine for the last 6 years ) The issue is when turning on from cold the boiler rapidly hit the max temp setpoint and knocks off (no fault indication though) - ie it seems that there is little in the way of circulation. I installed a cross-over within 3 m of the boiler to check oultet / return temp and this proves flow - which showed return flows. I've fully bled the system, stripped and checked the pump, yet it seems there is little active flow. The only other change was the removal of a radiator in the upper bedroom - a small unit with no thermostatic valve, therfore open to the system feed / return at all times - assuming this may have been the issue - I re-created this loop and it still didn't make a difference. I'm assuming that the minor changes in pipework may have increased head to the degree that I've got insufficient flow. The pump is integral and single speed? Add a second pump? Change the pump? Can't wait until mid Jan

 

[Agile]

The usual cause would be a blocked return filter at the boiler. Or a blockage at a valve or other restriction.

It can also be dirt in the eye of the pump.

But I cannot remember if your model has a return filter! Look in the manual if you have one.

Tony

 

[mickyg]

do when you bypassed the heating circuit did it work ok?

 

[Leakypipes]

Hi thanks for answering, when I put in a temp bypass there was a visible temperature ridse in both feed and return.
I don't think there is a filter - other thasn the retrun valve mesh - all clean. All new rads and all new valves!
There is an auto bypass valve in this model - could this be the cause??
http://www.protherm.lt/upload/download/1117195074.pdf

 

[Agile]

There is no mention of any heating return filter on those MI you linked to.

But makers dont always mention them but I dont see any evidence of them on drawings either.

Its quite common for bits to block the flow inlet on valves or anywhere else where the pipe is restricted.

Dirt can also block the eye of the pump!

Tony

 

[Gasinayr]

Are the hot & cold pipes connected correctly, not crossed over. Hot to cold connection cold to hot

 

[Leakypipes]

I did suspect that this may have been a possibility - ie the small bedroom rad which was removed was the cross over - I'm going to rip up all the flooring just to double check - I've got to admit after checking everything else I'm at a loss. The only thing I'm not sure of is the auto bypass valve on the boiler, I assume this is a thermostatically operated unit? mind you, if this was in operation, the inlet to the pump would be same temp.
Time to investigate further!
trace pipework fully t ensure no cross-over
Isolate system and flush to prove flow;
strip / check pump;
I'll keep you posted out of interest - many thanks - wishing you well for the New Year
Cheers Mark
(ps - I've a spare pump - what do you think to rigging up a temp booster? this would at least tell me if the losses in the system were leading to the low flow?)

 

[Agile]

Dont add any pumps, they usually stop the boiler from working and they are not necessary.

I dont understand this reference to crossover. That suggestion is normally in respect of the hot water supply and i8s not relevant to heating.

The auto bypass opens when the pump pressure exceeds a certain value as would happen as TRVs close.

It does have the effect of returning hot flow temperature to the return which can cause the boiler to cycle off more quickly. Normally this will not happen if its correctly set because most rads will be on and using heat.

In your case there seems to be a flow restriction. Checking the eye of the pump would be a first test. Together with a finger test to check the torque ( see FAQ ). If that does not identify the problem then it could be at a valve or other restriction where there is a blockage.

Tony Glazier

 

[Leakypipes]

Hi Tony, many thanks for your reply - given up trying to get warm - going to the pub.
OK - extra pump is a no no.
My money is on the pump - I'll strip it tomorrow once the hangover has gone
I'll be amazed if there is a blockage elsewhere as its all new rads and valves.
There is an oustide chance that there could be a cross-over ie a mix in the feed / return pipes - I'll re-trace the route again - it could well have been crossed over as the lines from the kitchen were moved and boxed in, so my mate could have had a brain freeze as the house has been upsifde down over these last few weeks (woodworm - cutting out floors and replacing whilst trying to keep items like a fitted kitchen in place lol )
Thanks again - wishing you all the best for the New Year
I'll let you know what I find
Cheers
Mark

 

[Agile]

Reversing flow and returns to rads has little or no effect.

If there is a direct connection between flow and return then the return at the boiler will equal the flow temp and the boiler will turn off as soon as it gets to temp and some/all of the rads will be cold.

Tony