Pitching after attic conversion

rufio777

Looking for some advice if possible…we’re almost finished an attic conversion (standard 3 bed semi built 1980)

The plumber has moved the cold water tank and the F&E tank into the corner of the attic and all seemed fine until we starting lighting the fire, from what I understand when the house was built the only source of heat was the open fire with back boiler, at some stage later then an oil burner was added.

when the oil is on everything is fine but when the circulating pump on the back boiler comes on water is pitching into the F&E tank in the attic.

Am I right in thinking the water level in the F&E tank sits at the same level in the expansion pipe it is pitching from? Ie/ if the tank could be lowered or the expansion pipe raised this might help?

I turned the circulating pump down to level 1 (was always at 2) and this seems to have stopped it but it’s not heating all the rads now.

What are my options here? We use the fire a lot and were strongly considering a boiler inset stove to replace it but in 2 minds now until I can figure this out.

Also to add, I got the plumber to install a larger hot water cylinder and a pump to help with pressure in the shower but not sure if either of these has an affect on the problem.

Thanks

stephenmarr

raise the expansion pipe if possible

10-10-20

...and/or try rebalance the rads and hope that you can get it done across the board with the pump on 1.

tb66

Presuming everything was ok prior to moving the f+e tank, as said above try raising the expansion pipe. Larger cylinder is unlikely to be the cause but if there is a coil in it to heat water from central heating and pipe work was altered/rerouted maybe this could be a factor too.

rufio777

Had another look yesterday evening, with the tank now in the corner of the attic there isn’t much room to raise the expansion pipe, maybe 2-3 inches, could this be enough to work? If doesn’t is there any other options that might?

Im pretty sure it wasn’t happening before as I would have heard it running in the attic. I’m no plumber but have a fair idea how the system works, however I can’t understand why it only happens when the back boiler pump is on, and not the CH pump? Oil burner is outside and it’s pump is and always had been on setting 3.

Thanks for help so far

Tails142

My thinking is the pump on back boiler is circulating water that's already circulating and is adding just enough head for water to flow up and over through the expansion pipe.

Pipe fittings and bends in pipe reduce head too so this is likely why you are having a problem now when you never had one before the tank was moved. The pipe work to the expansion pipe is now giving a smoother run to the water and it's allowing the pitching.

Turning down the pumps is the right thing to do if it solves your pitching. If rads aren't heating try rebalancing some of the rads that are heating, a quarter turn on the tail valves of the heating rads to try and redirect the flow toward the rads that aren't heating.

FYI, Ball Park, you are looking for about a 20c temp drop to run a system efficiently between the in and out on the rad tails so you could check this with a thermometer during the balancing process to see if there are any rads getting too much flow or too little.

tb66

As Tails said an extra fitting or couple mtrs less in length now could now be the difference. The previous vent was most likely higher than the current one. The outdoor pump has a lot more work to do to with the distance hence why no 3 works on it and it dosnt overpump but the indoor one depending on location may only be less than 5 mtrs from vent outlet and water will take the least path of resistance, so raising that to make it more difficult would be the obvious choice. If its just a tiny trickle a couple inches higher may work but you going to be on the overpump margin and turning down a red valve a bit could cause it again.

Rebalancing rads may work but with low circulating rate still no guarantee they will all reach suitable temp. Have you the option of extending the vent up roof as near to eave as possible and then reroute back over tank. If using Qualplex you may be able to just bend it, if not a couple of elbows will do the job.

10-10-20

If using qualpex then make sure to support it well in case it heats up and decides to droop.