Cold Feed Getting Hot

[burnssj]

I have an open vented CH system.

I've just had a new boiler, pump, electronic controls & room stat fitted. It's not been the best experience I've had.

Now the work is complete, I've noticed that the 15mm piped cold feed into the CH system gets hot from time to time.

Not sure how high up the "hotness" goes - I will be checking this weekend.

If anyone has any ideas what I should be doing to rectify this I'd be grateful.

I notice the pump has been set to 3 though. And the By-pass is slightly open for circulation because of TRVs on rads.

Don't really want to get the engineer back again as already stated (not the best time I've ever had).

Thank You

 

[Plamber]

would it be the heat from the boiler just going back down the pipe? how far is it going back?

Not a check valve on the boiler?

 

[burnssj]

The flow goes

Boiler
Open Vent
Cold Feed (from expansion tank in loft)
Pump
And then I think it's the 3 way valve & by-pass circuit

So the hot water is pulled past the vertical open vent & vertical cold feed & then on round the system, but the vertical cold feed gets a little warm, then hot, then stone cold etc.

I am going to check the expansion tank in the loft to make sure the warm/hot is not going all the way up as I understand moisture in the loft is a very bad thing.

The pump is set to the highest setting. I did wonder if that's part of the problem though I am also concerned if I turn the pump down that the heat may not be "got away" from the boiler fast enough

 

[Plamber]

so the feed from the FAE tank to the boiler is the one heating up?

 

[Blackcatgas]

The water in your system expands by 4% when the heating is on, the water expands back up that 15mm pipe and raises the level of the water in the tank, the whole tank can get warm from the heat rising.
perfectly normal.

 

[helpsy]

Also you said bypass open slightly-shouldn't it now be an automatic bypass?

 

[burnssj]

The boiler is in the garage. The feed tank is quite some distance away in the loft feeding into the circuit.

I think someone told me that for every 21 gallons of water in the system, you get 1 gallon of expansion? (not sure it that's true).

The heating comes on, pump (now it is in the right place on the circuit) drags water past the open vent and the cold feed.

Cold feed, on occasion, gets warm, sometimes hot, then freezing cold. It may just be expansion from the water for the CH heating up and so it's taking the open vent and the cold feed pipe as a means to expand. And the pipe is only 15mm and copper... I wouldn't have thought the cold feed pipe could go from warm or hot to freezing cold if the water in the feed tank was warm or hot as my understanding is that pipe is filled with water all the time?

Anyway, I sent the boyfriend up in the loft yesterday morning and he said the water in the little feed tank is tepid - not hot or even warm - and that's when the 15mm pipe was hot. His words were "it's tepid, but I wouldn't want to wash in it, it's not warm enough for that". So I think it is OK. It's certainly not making a radiator in the loft nor pumping over.

I think someone else commented that because of expansion and the size of the pipe that it's perfectly normal for hot water to travel up & back down it periodically? Heat transferral or expansion perhaps?

It's just with all the hassle I've had having the new boiler fitted (right from the fitter going to provide the boiler electrically in a completely inappropriate method, to the pump being moved before the open vent and having to be moved back again), I was looking for expert opinion/advice/reassurance that what's happening isn't unusal. This cold feed pipe may well have got warm with the old boiler on. My neighbour tells me his gets warm and he has a the same basic system (same house).

I must say though, you have all been very helpful.