Hot rads in summer

I have an oil fired heating system based on the Honeywell S plan ? a pumped system with separate zone valves for the hot water cylinder primary and the radiators and I'd appreciate advice.

Issue 1: The 22mm return pipe is common to both the cylinder and the radiators and most of the system converges just near the cylinder outlet. The radiators get hot by convection from this low point even if no room heating is needed. Is an independent return pipe for the cylinder my only solution?

Issue 2: The present vent pipe from the top of the boiler follows the same heating run and has a huge U section in it ? ie it goes down about

3 metres before climbing to the loft. Total horizontal run is about 15 metres. _____ Present Vent pipe: ! ! vent ! ! Boiler_top______ ________! ! ! ! ! ! _______! !______!

Am I right in thinking that even this arrangement is unsatisfactory, much less one involving re-use of part of the vent pipe for the cylinder return and connection of the new vent at the cylinder primary outlet which is 3m below the boiler? Like this:

_____ ! ! vent ! ! Boiler base------

Reply to
P.R.Brady
Loading thread data ...

If all the radiator returns converge and then join the main 22mm return at one point, then this should be enough to prevent parasitic convection. If this is already the case, suspect the zone valve.

This is extremely dangerous. I would not use the boiler in this condition. I would only really consider it if the boiler was stated as suitable for sealed, pressurised operation (i.e. manual reset overheat cutout) and had a pressure relief valve close to the boiler. This way, it is not relying on the vent for safety. However, if you are going this far, you might as well do the full sealed conversion.

Christian.

Reply to
Christian McArdle

You may well have already noticed, but you sure as hell do not need your rads on right now....phew!

Reply to
RedOnRed

The zone valve was my first thought and it was stiff to operate so I've replaced it. The new one is working fine. The rads are actually spread out along the return run - 4 upstairs, downpipe to the cylinder 'out' pipe, 2 just near the cylinder then 5 on way back to boiler. I've felt the pipes and it's definitely 'parasitic' - the CH feed stays stone cold.

Christian - Are you saying that the U is dangerous, or the 15m horizontal? Would an __almost__ horizontal pipe out of the boiler,

15m along under the bedroom flooring, then up to the header tank be satisfactory? I could then re-use the old venting pipe for the cylinder return.

Fully sealed is an interesting possibility! I will check in the manual but it certainly does have such a reset.

Regards Phil

Reply to
P.R.Brady

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.