hot water on only when heating on.

[jase158]

Hi All,

Went to a property today, powerflushed system as hot water not heating up.

(customer told by BG needed power flush)

Then when finnished, fired up boiler and had heating and hot water on, everything fine.

Then turned heating off and boiler switched off.

very strange and puzzling.

2 port valves working & pump working.

strangely enough, when just flushing the hot water circuit was getting no flow, however when I flushed with heating circuit on it gave good flow rate.

now I hear you cry, blockage in the hot water circuit, but I could hear the hot water circuit having water pass through it, so couldnt be that. and when I turned heating and hot water on, the pipes got really hot.

Finnally fully pumped, vented system, if You hadnt already guessed with old cast iron floor standing boiler.

What would cause this? my guess is some sort of wiring fault but unsure.

 

[jase158]

forgot to mention was 15mm pipes to cylinder and changed to 22mm just outside cylinder, flow and return

 

[SimonJohns]

Prob got a check valve stuck. By doing the wrong circulation you could have stuck it closed

 

[jase158]

check valve in central heating? never heard of that?

anyways, how would it work when central heating was on but not on its own?

doesnt make sense to me, but thank you for your suggestion.

 

[SimonJohns]

Sorry. Didn't understand that the hot water worked when the heating was on

Does the pump work on hw?

No other reason for it not to work if 2 port is opening etc

 

[jase158]

yeah i believe so,

thats what i thought, very confusing

 

[bambers]

If the water circulates through coil when the heating is on it has to be a control problem with the h.w. 2 port valve / wiring issue, what make of controls have you got?

 

[jase158]

not sure mate, Customer is covered by BG so I advised that he get them out to sort out, but just wondering if I was missing something obvious.

I was thinking that maybe the 2x 2 port valves were wired up wrong but customer was adement that it worked before and that there was no work done since it was working.