Vaillant TURBOmax 242/282 Heating coming on with H/W

[wedge69]

We have a Vaillant TURBOmax 242/282

I was upstairs in our house while my wife was running the hot water downstairs in the kitchen, and I noticed that one of the pipes to a radiator was getting hot.

Looking at the boiler, the light was on for hot water, but the central heating light was off. The flow central heating pipe from the boiler was very hot.

Any ideas what the problem could be. I thought the heating and the hot water were two seperate systems with this boiler? Can the hot water be somehow entering the central heating system?

Cheers

 

[twgas]

sounds like a diverter valve problem

 

[Deleted member 105431]

diverter valve part no 252457. Vaillant do it for £215 fixed price

 

[wedge69]

Thanks for the help.

Can someone just give me a quick explaination of how the diverter valve works then? I mean, does it take two inputs (one from mains cold, one from central heating feed) and have two outputs (one to dhw and one to central heating flow)?

So if my diverter is faulty it is taking in mains cold water, heating it up, sending some to the taps and putting some into the central heating system? Won't this increase the pressure in my heating system?

And when you sat Vaillant do it for £215, is that fitting as well? Is there a website or a number to ring?

 

[Gasguru]

The diverter diverts heated primary water (from the main gas to water heat exchanger) between the radiator circuit and the secondary plate heat exchanger. The domestic (secondary) water is seperate from the primary water but heated in the plate heat exchanger.

Instead of fully diverting the primary water the valve is allowing partial water flow in each circuit.

 

[namsag]

Basically two outlet ports when its just on HW the outlet port to CH should be sealed closed so if its getting hot when HW is ON then it is not properly sealed and is passing.
If its a couple of rads getint hot straight after HW demand has gone off this could be due to pump over run to get rid of heat out of the boiler

No pressure won`t increase with this fault
BGwill do this fault for fixed fee of £165 and yes both prices include fitting

 

[wedge69]

If its a couple of rads getint hot straight after HW demand has gone off this could be due to pump over run to get rid of heat out of the boiler

Well I've had a look today, just after filling up the sink for the washing up, I went to the boiler. No radiators were hot, just about a foot of the central heating flow pipe from the boiler, so I guess this could be what you said above - pump overrun?

Filling up the sink for the washing up only has the water on for a short time, obviously. We are having our bathroom done at the moment, but I will be able to use the shower on Wednesday, which will mean drawing the hot water for a long time. So I guess after my shower I can see if it's just a bit of the central heating pipe that has heated up (no problem) or whether a few radiators have got hot (probably a diverter problem).

I really appreciatge everyone's help on here!