Hot Water Problem - blockage in primary circuit?

[rsr]

Morning All

On investigating my wife's complaining that the hot water is not as hot as usual it seems that the issue is with the primary circuit.

The system is Y plan with vented HW and unsealed CH which is pumped. On demand for HW the primary to the cylinder is well hot but the primary return is cold. Presumably a blockage of some kind?? I've ruled out an air lock as there are no issues with circulation.

Is there anything I can do before I have to replace the HW cylinder? It must be at least 15 years old and we're in a hard water area.

Cheers
RSR

 

[ecowarm]

When you say no issue with circualtion, there is obviously. Check the small tank in roof or top of cupboard the F&E tank. It may have run dry, seized ball valve.

 

[warrington]

Is there any problem with the heating?

 

[rsr]

F&E Tank fine and heating also fine.

Possibly a hole in the cylinder coil???

 

[grahamgas]

If you had a hole in the coil, then surely your hot water at the taps would be discoloured, plus the f and e tank would be losing some water and topping up, plus eventually would be expanding up the vent pipe from cylinder, to cold water tank in loft

Must be a blockage of sorts, in the coil.

 

[diamondgas]

rsr, something worth checking is the diverter. On hot water only the flow should be through the cylinder side of the valve only! It could be that it is stuck just partially open and flowing mainly to the heating? Just a thought! Also, whereabouts are your open vent and cold feed tee'd in? It may well be the coil on the cylinder but could be a restriction on the hot water flow or return pipes IMO.

 

[rsr]

Thanks to all responders.

Diamondgas - there is an issue with the diverter. It will not switch to HW only. It's been like this for ages but we've always managed to get HW in mid position. Unfortunately the installer put the diverter in a totally inaccessible position and I'm trying to avoid attempting to change it- to do so requires someone to hold my feet so I can get to it from above.

To be clear the primary flow is hot at the entry boss of the cylinder but at the return it's cold. CH circuit is fine.

I think any one or more of the following explain what is happening:

1. diverter not dedicating enough to primary circuit
2. blockage in coil

If anyone has any other views I'd be pleased to hear.

Fortunately, the immersion is working.

Cheers

RSR

 

[diamondgas]

Thanks to all responders.

Diamondgas - there is an issue with the diverter. It will not switch to HW only.
RSR

Do you know the manufacturer? Nearly all diverter heads can be removed to expose the cam underneath. The actuator heads are replaceable too rsr. If the head has stuck it can be replaced, if it's the cam that's stuck then you may need a whole new valve Either way I'd personally want to verify what was happening when the valve was on hot water only?

By the way I once hacked a hole in someone's wall to access a pump behind a cylinder, much less costly than removing their cylinder & altering the pipework! They then got a joiner in to build a permanent access hatch

 

[rsr]

Diamondgas

Thks again. It's a standard Honeywell 3 port. I've got experience of changing the head and /or the whole valve. It's crazy but this one is right next to a wall hung boiler in an airing cupboard. The bottom of the boiler has about 150mm clearance so virtually floor standing. The cylinder and pipework prevent access to the 3 port other than from above and it's against an outside wall. Looks like I'm due for a cylinder change when we can afford it and I'll sort the 3 port then.

Cheers
RSR

 

[diamondgas]

Diamondgas

Thks again. It's a standard Honeywell 3 port. I've got experience of changing the head and /or the whole valve. It's crazy but this one is right next to a wall hung boiler in an airing cupboard. The bottom of the boiler has about 150mm clearance so virtually floor standing. The cylinder and pipework prevent access to the 3 port other than from above and it's against an outside wall. Looks like I'm due for a cylinder change when we can afford it and I'll sort the 3 port then.

Cheers
RSR

You're welcome You should get about £50 scrap for the cylinder... I hope a new diverter solves the problem. It does sound like the most likely suspect imo