Pumping over

[martin43]

Hi all

I wonder if the heating engineers could assist me.

I am fitting a cyl stat and 2 port valve for the DHW. The boiler is in the coal shed as is the pump (in the ret). F&R are teed, one side goes via the grd flr then upstairs and feeds all the rads. There is a 2 port valve in the CH flow. The other side of the tees goes up to the attic, tees again with one side to the cylinder with 2 port valve in the ret. The other side of the attic tees goes to the F&E cistern, F on ret and vent on flow. If the valve on the cyl is closed then the system pumps over via the vent into the F&E. The cylinder is on the attic floor, the F&E is 6 feet higher, the vent goes to the pitch of the roof. Any ideas how to prevent the pumping over please?

Thanks
Martin

 

[Soggy_weetabix]

Presumably, h/w is pumped too?

Can you not plumb in a close coupled or combined c/f o/v configuration.

I'm sure piccies are available on this site.

David

 

[jobloggs]

You have a common configuration from the time before control valves. If you insist on a zone valve on the HW circuit then you will have to provide new feed & vent pipes back to boilerhouse as soggy says. Biggish job!!

You will also need to move the pump to the flow side of the boiler with feed & vent pipe(s) teed in between boiler and pump.

 

[martin43]

Thanks to jo and soggy for their helpful info. Can I do the following, move pump to the boiler flow, provide new vent teed in between boiler and pump, retain existing F&E teed into cyl ret. I appreciate it's not wholly satis but there is a problem in getting additional pipes into the duct up the kitchen wall. Since I've got the bathroom stripped out, now is the time to do it.

Thanks
Martin

 

[jobloggs]

You could run a single combined F&V pipe in 22mm minimum between boiler and pump on the flow side and cap off the existing feed & vent pipes in the attic.

If you retain the separate feed in attic this should be teed into return after the 2 port valve

 

[martin43]

Thanks for the suggestion Jo, but after a further study of available space to get additional pipework in without rebuilding the kithchen, I can't. It's really only come about because the DHW storage temp is too high during the winter, and whilst other works are going on it seemed an ideal time to tackle it. Hey ho.

Thanks anyway

Martin

 

[ollski]

Would it not be easier to simply convert it to a sealed system

 

[ChrisR]

WHat's the boiler - bet it's too old to go sealed.

Easier than that. Feed pipe joins the return at the cylinder does it??Connect the feed from the F&E to the vent, wherever you can reach it. Right by the cylinder would be OK. Put a manual bleed valve on the old feed pipe which went to the boiler.
That gives you a combined feed and vent so no loop to pump round.

If the boiler boils it's asking a lot for the water to get down the flow pipe with the steam coming up, though we're told it will. So I'd clamp an extra thermostat on the flow pipe by the boiler, set to 95. Honeywell do a manual resetting one (IE you have to press a button)

 

[martin43]

ollski

v good idea, however the cyl was replaced 4 years ago so its still quite new, in turn it replaced a primactic so i could add inhibitor, also to provide balanced supply for mixer shower. Boilers ancient as well, see below.

Chris R

Boilers an Ideal E type RS at least 9 yrs old, however in its defence, its b simple, one thermocouple in 9 yrs is my idea of reliable appliance. How compliant is a combined feed/vent with Scottish B regs, does it matter? To make sure I understand correctly, the ret has the feed plus vent, flow has air vent only?

Thanks both

Martin

 

[ChrisR]

No, the return gets nothing. If you stooge around some online boiler manuals you'll see it done a lot, but modern boilers have an overheat thermostat which yours might not.
small words in the middle say "man air vent"

Do yo have a lot of trv's? You wouldn't normally get pumping over if the CH circuit is fairly free, unless it's sludged up??????
Hopefully your valve(s) both turn the pump off when there's no demand....??

 

[martin43]

Thanks for that Chris, understood now. TRV's on all rads, boiler controlled by stats and valves. It could well be sludgy, however there is no problem with any of the rads heating up, even the last one on the system. Do you think the difference between the static and dynamic head and the height if the vent above the F&E has abearing in this?

Regards
Martin

 

[martin43]

Thanks to everyone who gave their thoughts, it was most helpful. I have decided that the best course is to wait until the boiler needs replacing then convert the whole lot to a sealed system.

Martin