Regular Boiler - CH OK but water only gets tepid

[shooey]

Hi,

I've had this problem before, and it somehow went away on its own, but now it's happened again. I've got a regular boiler, F&E tank in my loft and a cylinder tank in an upstairs airing cupboard. The CH has always been fine, but the water was taking longer and longer to heat up until now it never gets more than tepid.

Into the cylinder tank goes 2 pipes which are level with each other. One gets hot and everything beyond it is hot. The other is cold and everything beyond it is cold.

Any suggestions on things I can try, or some background info that might help me understand?

Many thanks

 

[terryplumb]

The two pipes that you refer to ,going in to cylinder at top ,are connected to a heat exchanger inside the cylinder ( bit like a radiator in there ) its that what heats the water around it. You have no flow through through it ,its probably blocked. It looks like a very old set up.

 

[shooey]

Thanks terryplumb, and yes it is a very old system.

So both pipes should be hot then?

If it is blocked then, is there anything I can do to unblock it?

Thanks

 

[terryplumb]

The two pipes are connected to the flow and return pipes of the boiler. ,the pump delivers water ,heated by the boiler, through the flow pipe ( which is the hot one ) and it runs through cylinder exchanger and out the other pipe returning to the boiler. So yes they would both be hot under normal running conditions. If there isnt a total blockage ,but a severe restriction ,you will get domestic hot water at a very low temperature ,and limited amount. Are there any motorised valves on your pipework ,none in your pic , they would have an electric cable running to them .

 

[shooey]

Thanks again. No, I don't think I have a mororised valve - that green tap/gate in the very bottom corner is supposed to allow me to switch between CH/HW, but doesn't seem to do much. Also, I noticed this morning that the overflow pipe (in the loft near the F&E tanks) in dripping water???

Thanks

 

[terryplumb]

You will need to get into the loft and check which tank is overflowing. The large tank supplies water to hot water cylinder ( possibly some cold taps and wc ) the small tank supplies c/ heating and boiler and is called the feed and expansion tank ( f & e ). The water going into the tank are Controlled by a ball cock ,and if they dont fully close water keeps going in until it reaches the overflow. Quite common with age that they need attention or replacing. The f&e tank has one ,but other things can cause the level in there to raise but first thing to check is the ball cock.
You mention a green gate valve that is "supposed " to allow you to change between ch and dhw. Is that the only thing you have to enable one or the other ? So in summer when you want only dhw and no ch ,what do you do ?
Gate valves are notorious for failing to either fully close or fully open

 

[ianmcd]

you have what I call a Hot water Blade as that is what it was called when I was an apprentice 30 years a go, was designed to go into an immersion heater socket in your HW cylinder, very prone to airlocking but could be blocked as will be very old , no reason why it cant be cleared though , more so if you still have some circulation ask an experienced engineer to help you out , not a youngster who puts an analyser in your boiler and tells you that you need a combi

 

[shooey]

Thanks both.

I will check the tanks again since it's started overflowing, but I think they're OK as I'd already checked them a few nights ago when it first started.

So if it is a blockage, there's nothing I can try myself? Forcing cold water through the hot water pipes (via mixer tap) wouldn't help? (It's the only plumbing trick I know)

Thanks

 

[terryplumb]

You could try adding a chemical cleaning agent into the system ,it may just work .cheap enough to try.

 

[shooey]

Thanks terryplumb

So would I be adding the cleaning agent to the large tank then?

Thanks

 

[terryplumb]

NO ,you do NOT. It would go into the radiator system ,via a radiator or the f&e tank , which you must sort out the possible overflow issue on first ,and lower the water level.

 

[shooey]

Thanks

 

[shooey]

Hi - it's me again...

So, I've emptied my F&E tank with a jug and a bucket, and thoroughly cleaned it inside, and then added some Fernox.

My question now is, what causes the contents of this tank to filter their way through the system, and hopefully into my HW cylinder?

Because nothing seems to be causing that tank to drain and refill. I've tried putting the heating on, and I've tried running a hot tap, but nothing seems to happen in my F&E tank???

Thanks

 

[JohnD]

you have to draw a bucket of water out of the drain cock at the lowest point of your heating system.

It would have been better to do that before adding your chemical.

Which chemical did you use?

 

[ReganAndCarter]

you have what I call a Hot water Blade as that is what it was called when I was an apprentice 30 years a go,

Also called a microversion. Clever way of converting an existing direct cylinder into an indirect cylinder using the immersion hole. Not many about now.