NO HOT WATER/CH WORKING

[B C]

Hi appreciate some advice- SYSTEM WORKING FINE TILL I recently removed a radiator for decorating after replacing,had no hot water but ch ok I have a conventional wet system, 3 port valve pump/ cylinder stat/ drained system also replaced port valve and cylinder stat bled rads. Iam guessing its a air block but cant figure how to shift the b*%$*&d when timer calls for ch ok but no response for hw. pipes are hot at ports but cold going into cylinder, any opinions would be greatly appreciated

[Andy Hall]

Are you sure that you have wired the 3 port valve correctly, and have you got the correct replacement? There are diverter and mid position types.

Your comment

"when timer calls for ch ok but no response for hw. pipes are hot at ports but cold going into cylinder"

is a bit cryptic. What do you mean? Which ports? Can you expand this a little bit, please.

You could try taking the motor head off of the 3 port valve and operating the cam manually - e.g. with the CH on. See if the cylinder coil starts to receive heat.

If there is a high point on the cylinder coil connections (i.e. pipes come from below) there should be a means to vent it at or near the upper connection. If somebody was lazy when plumbing then this could explain your problem. It's easily fixed with a small manual air vent. e.g.

part no. 6793. You would arrange one of these on the top of a short branched piece of

15mm tube teed onto the upper cylinder connection.

.andy

To email, substitute .nospam with .gl

[Set Square]

Silly question: I suppose the new cylinder stat *is* set correctly and not turned right down? Ok then, well is it *wired* correctly - bearing in mind that it's got (or should have!) changeover contacts. [If these are wired the wrong way round, the 3-port valve will only feed boiler water through the indirect coil when the cylinder is *hot* - so it never gets hot!]

What length is the pipework between the 3-port valve and the hot cylinder? Is there a gate valve somewhere in it to balance CH vs HW when they are both on? Is it turned off? [Might you have turned it off when you drained the system, and then forgot to turn it on again?]

[B C]

thanks for taking the time to answer,re/cylinder stat/ Iam sure it is wired ok and temp set correctly, pipe work is a short run to cylinder with a bleed spured of it which I have bled. the pipe from 3 port/v into cylinder remains cold and I also have a radiator which is hot at base cool at top which cant be bled due to there being no bleed valve apart from this and my wifes mood central heating works on demand.

[Set Square]

Does your 3-port valve have a central position where it feeds CH and HW at the same time - or is it a diverter valve which only produces one at a time?

Have you tried removing the actuator from the valve, and turning it manually to see whether the pipe to the cylinder then gets hot?

If no water is flowing to the indirect coil in your HW cylinder this has to be due to one of two basic causes - either the HW port on the 3-port valve isn't opening or it *is* opening but there is an airlock or blockage in that part of the circuit.

If you have well and truly bled that part of the system, and have made sure that there are no gate valves turned off, the second cause seems unlikely - so it's best to concentrate on the first. If you can get HW by moving the valve manually when the CH is on, that would confirm that the problem is in the valve control system. If the valve never goes to the HW position, this could be due to:

• seized valve (unlikely if it's new)

• faulty actuator (Also unlikely - and its spring return would likely take it to the HW position anyway)

• No HW demand from the programmer

• No unsatisfied HW demand from the cylinder stat

• Incorrect connections to 3-port valve

As you have apparently just changed both the 3-port valve and the cylinder stat, I would put my money on the wiring of these. Do all wires come together in a 10-way junction box? Assuming it's a mid-position valve, have you verified the connections by looking at the Y-plan details in

?

Regarding your radiator with "no bleed valve". Sounds unlikely! Some radiators hide their bleed valves fairly well by putting them near the top of the back face rather than at one end. Feel along the back over the top edge - or have a look with a mirror.