Need help with a hot water problem

[thebaronn]

Hi all, I have a problem with my DHW system which is not as old as the house, but it seems to behave that way! I'm looking for some advice on a problem I have with HW; ideally I'd like to know what's wrong with it, what needs replacing/repairing and how much it is likely to cost (parts and labour). Here is the problem...

First of all the setup, it's a typical system for when the house was last refurbished; cold and expansion water tanks in the loft, hot water cylinder w/immersion in the airing cupboard, boiler in the kitchen. I have had several other (hopefully unrelated) issues over the last year or so, so have ended up replacing the 3 position valve, room and tank stats, as well as the programmer (which is separate to the boiler). Components are pretty standard, Honeywell valve and tank stats, Horstmann programmer and room stat. The boiler is an Ideal Classic FF360.

We seem to have no problems with the CH (famous last words!). The new programmer and room stat also seem to be working fine (we also have some rad stats, but tend to leave them on full or off). However, when we programme HW, the burners in the boiler fire up, stay on for a couple of minutes and then cut out. We have been relying on the immersion for the last few days for HW, which is working fine and seems to be giving us a full cylinder's worth.

Any ideas would be gratefully received. My thoughts so far:-

Could the plumber have wired the 3 position valve incorrectly/loose connection?
Is a stat in the boiler malfunctioning?

Any advice appreciated, cheers.

 

[RickMoore]

Is the valve moving into the correct position ? Does the flow pipe to the cylinder get any heat to it at all ?

If this has just been done then I would get whoever did it to come back and sort it out.

 

[matt1e]

As above get whoever changed the valve to come back and sort it,
If the central heating is working ok then it's likely to be an airlock in the cylinder coil causing what you describe
Either way the last engineer should have checked all was working ok before he left anyway

Matt

 

[bazdaman]

Did plumber drain down to change 3 port? Ithere an air vent on the cylinder pipes? If u r not sure a pic of the cyl pipes would help?

 

[thebaronn]

Thanks for the swift replies guys, all really useful.

@RickMoore, the valve moves into the "Auto" position. Shall I take the shielding off to see the valve in action? The problem is, the boiler cuts off after a minute or so when in HW only mode (if it comes on at all). Should I put CH and HW on and then check the valve/flow pipe? After the valve was fitted it was working for a period, cant be sure for how long. We previously had HW when the CH was on (when it was colder) so there wasn't a problem. In the warmer months we have used the immersion as and when we needed HW.

@Matt, I recall that it was working when the engineer left, albeit that there was an airlock in the CH which we always get when the system is drained(old house, old pipes)

@Badzaman, I believe that he did drain it down.

Bleed valve and 3 position valve

• thebaronn
• 28 Sep 2013
• 1

The bleed valve gives water straight away.[/img]

 

[thebaronn]

Bump. Just another thought, I have made sure there is no hot water in the cylinder (from the immersion). I have now set the 3 way valve to manual (open) and switched on the HW only. My thinking is that the rads should heat up, but, if the valve is where the problem is then I should not get any HW (unless it is the cylinder)?

With the valve set to manually open, the boiler at least now fires up and stays on. Will give it a few minutes to see if I get any HW. The pipe to the cylinder is now getting slowly warm, unless that's heat transference?

 

[Hugh Jaleak]

With valve in mid position then both pipes should be getting hot, the HW connection to cylinder possibly more so as there may be less resistance for the pump to push the water round the cylinder coil than the radiators....

Valve should rest (i.e. when system is off) open to HW anyway so if HW hasnt worked previously then I would suggest problem lies in the cylinder, either airlocked or blocked coil. Your symptoms are those of little or no circulation around the cylinder coil. Fact boiler is continuing to fire would correspond with the heated water getting around the heating circuit, I would suspect if valve was allowed to go back to auto (rest position if CH is off) then boiler will soon cut out again.

 

[thebaronn]

Cheers Hugh. So, after leaving the valve in manual for 20 minutes or so... no hot water at all. I switched the valve back to auto, heard the valve move, and the boiler cut out shortly thereafter (as you predicted). Airlock / blockage in the cylinder is looking like a strong possibility, other than that could there be a wiring fault? The cylinder is pretty ancient, so could well be that. Appreciate all the help by the way fellas, I want to make sure I tackle the right bit, don't have the spare cash to start swapping bits out. If the cylinder has an air lock or blockage, what are the best courses of action?

 

[Hugh Jaleak]

Wiring problem would manifest if one side wasn't working as it should, however with valve opened manually and boiler and pump running then the heated water should be going in both directions, i.e. to cylinder and rads. From your description so far it does seem there is a physical blockage preventing the water from heading through the coil.

Has this problem slowly appeared (water taking ages to heat via boiler) prior to valve swap or since the valve was changed? I also assume valve was fitted correct way round! (HW to port A, CH to B.)

 

[gigz]

I also assume valve was fitted correct way round! (HW to port A, CH to B.)

Other way round methinks
CH -port A
HW port B

 

[bazdaman]

Remember B for bath!

 

[thebaronn]

Just for my own sanity, checked the wiring to both the tank stat and the 3 way valve, and it looks good (ref Y-plan system). Honeywell tank stat L641A, Honeywell 3 way diverter valve, both wired to standard 10 terminal junction box. Tank stat to terminal box as follows (C to 6, 1 to 8, 2 to 7). Valve to terminal box (blue to 2, green/yellow to 3, white to 5, grey to 7, orange to.

Looks like airlock in the cylinder/blocked cylinder sound the most plausible. But wait...

Looking at the actual valve (the brass bit, not the motorised part), port B leads to the bottom of the cylinder, port AB leads to the pump (then presumably the boiler) so I assume port A, which goes through the floor, feeds the CH. So, is this definitely the wrong way around? Model of the valve is a Honeywell V4073A1039 Sundial Y Plan 3 Position Diverter Valve.

The thing is, I am sure that after it was fitted it worked for a period. Is this possible? Truth is, it has been like this for a long time have been making do with the immersion (sparingly).

 

[gigz]

See two posts above

 

[thebaronn]

Phew, cheers Gigz and Bazdaman, at least that's correct.

So, where were we, as Hugh diagnosed, looks like airlock in the cylinder/blocked cylinder sound the most plausible.

Any suggestions to remove the airlock and/or blockage? I recall hearing that you can get fluids to flush through, but that they can expose weak points in old pipework, and by the looks of this boiler/cylinder, this is pretty old!

 

[gigz]

Looks a bit awkward due to orientation of your cylinder but you could see if the coil could be poked out to clear blockage, doubt it's air if you're getting water from bleeder.