CH System - All Rads Cold - Possible Pump problem

[Tezbedz]

Hi
Woke up this morning to a cold house, no heating.

We noticed a problem last night, we turned the thermostat up but the heating did not come on. I switched the water heating off, and switched the CH off and on and the pump started and rads warmed up.

This morning nothing. Water was hot, so switched off water changed the thermostat, switched off and on but nothing.

Pump was making a humming/buzzing sound and was hot.

Triple port valve, moves correctly (or the little indicator thing does) left hot water, centre both, right CH.

The system is an open system.

I removed a rad a couple of weeks ago to clean out as bottom of rad was cold.

I am sure it needs flushing, cleaning and then inhibitor put in as I don't think this has been done for years.

I think I replaced the pump last year, but am not sure as cannot find receipt, certainly in last 2 years.

Could the pump be jamming (no bob marley jokes please) by that I mean the pump is trying to pump crap round the system will that jam it?

If I remove the pump can I test it?

Is there anything else I can do?

My brother in law is a plumber/gas Fitter but is in benidorm until weekend (good time to go when winter sets in with a vengeance)

Thanks for any help you can give

 

[D_Hailsham]

we turned the thermostat up but the heating did not come on. I switched the water heating off, and switched the CH off and on and the pump started and rads warmed up.

This morning nothing. Water was hot, so switched off water changed the thermostat, switched off and on but nothing.

Pump was making a humming/buzzing sound and was hot.

Triple port valve, moves correctly (or the little indicator thing does) left hot water, centre both, right CH.

Pumps should last more than two years - even the cheap ones - so, as it was working when you turned the system off and back on, I suspect a problem with the mid-position (3-port) valve. Unfortunately the indicator on the side is no guarantee that it is working correctly.

You should test the components in sequence - timer(s), thermostat(s), mid-position valve - to identify the cause of the problem. See Honeywell Wiring Guide for detailed fault finding procedure.

 

[Tezbedz]

Thanks for your prompt reply, I have downloaded and printed the guide you suggested. Will see what I can do myself from there, I am not sure if wiring will be same colour as ours is an old system, at least 20 years!

Is there a way of checking if the valve is operating correctly, apart from the pipes getting hot?

As the fault seems intermittent it could be a dodgy electrical connection to either the pump or from the 3 port valve, I will have a look at those this evening.

 

[MANDATE]

The comments below are based on the valve going to CH position and not lighting boiler.
You'll not find anything wrong with the pump because you're getting HW.
What I believe is happening is this! You set it for both HW and CH and both are in demand, so boiler lights and you get HW and CH. Now HW gets satisfied reasonabley quick but CH does not. As soon as HW is satisfied valve moves over to CH only and boiler should light but in your case nothing happens.
The explanation is this. Whenever the demand involves HW, the cylinder stat provides the power to light boiler. If HW is not on or is on and satisfied the cylinder stat no longer provides that power, so power comes from a different source. That different source is from the 'orange' wire of the 3 port valve. Now it does not come from yours because there is a faulty micro switch in the head of the valve.
Now to prove this have both HW and CH on and feel the CH pipe about a couple of feet away from the 3 port valve. This needs to be done when HW is satisfied and boiler will have stopped waiting for cylinder temperture to drop. The CH pipe will be cool.
Now heres the simple test either (a)turn the the cylinder stat up or (b)just run some HW off.
This will create a HW demand and boiler will re-light and you will now find the CH will now get hot. But it won't be on long, just till HW is satisfied again. This is why you think its a intermittent fault.

 

[Tezbedz]

Hi Thanks for your reply, I have now got home and have discovered more about the problem.

The programmer switches both HW and CH on at 16.30 before this my wife had managed to get CH by twiddling thermostat and switching CH on and off at programmer.

When I got home the CH was off. The 3 Port valve was in the central position. I got my wife to switch HW off at programmer. 3 Port Valve moved to right, pump came on and CH to all radiators.

The CH has since shut itself down, the thermostat and programmer are still indicatng "on" and the 3 port valve is still pointing to the right.

Does this mean the 3 port valve needs replacing?

Is there a way to bypass this problem to switch CH on, until I can confirm what needs replacing and to get the new part?

 

[MANDATE]

When I got home the CH was off. The 3 Port valve was in the central position. I got my wife to switch HW off at programmer. 3 Port Valve moved to right, pump came on and CH to all radiators.

I can't see how with CH off the valve could be in the central position unless its stuck there, which I dont think it is.
If CH is off then HW must have been on on its own. It only takes up the central position when HW and CH are both on and in demand. When one of those demands is satisfied the valve moves across to open fully the port still in demand. Maybe you should re check that aspect.
I still think it's a micro switch problem with dirty or burnt contacts, although it appears to have functioned correctly on one occasion.
The room stat will turn off the power that feeds the orange wire that lights the boiler, but the internal motor remains energised and the valve will stay there waiting for the room stat to bring the power back on. The only change to that would be if HW was demanded. Power holding valve would be cut and valve would unwind to HW position to meet the demand.
Most 3 port valves dont need to be changed completely. If you just change the head, you get new micro switches and new internal motor.

 

[Tezbedz]

I have found the following on screwfix is this valve ok

Drayton MA1/679-3 £ Port motorised valve for £58.71 less 10%

B & Q do a Sunvic SDMV2304 for £40.68

Which would be best?

 

[Tezbedz]

When I got home the CH was off. The 3 Port valve was in the central position. I got my wife to switch HW off at programmer. 3 Port Valve moved to right, pump came on and CH to all radiators.

I can't see how with CH off the valve could be in the central position unless its stuck there, which I dont think it is.
If CH is off then HW must have been on on its own. It only takes up the central position when HW and CH are both on and in demand. When one of those demands is satisfied the valve moves across to open fully the port still in demand. Maybe you should re check that aspect.
I still think it's a micro switch problem with dirty or burnt contacts, although it appears to have functioned correctly on one occasion.
The room stat will turn off the power that feeds the orange wire that lights the boiler, but the internal motor remains energised and the valve will stay there waiting for the room stat to bring the power back on. The only change to that would be if HW was demanded. Power holding valve would be cut and valve would unwind to HW position to meet the demand.
Most 3 port valves dont need to be changed completely. If you just change the head, you get new micro switches and new internal motor.

I am sorry, when I said the CH was off, I meant it was not working.

To explain a bit clearer.

Both HW and CH were switched on at Programmer, Room Thermostat was on, HW was hot, but CH was cold.

I switched HW off at Programmer and £ Port Valve moved from Centre to Right. Pump came on and CH started Rads getting hot. Checked about 1 hour later and CH was not working, (On at Programmer and Thermo, 3 Port still to right)

Thanks for your help

 

[MANDATE]

Ok that makes sense now!
What make is your existing 3 port valve?
If you just change the head it will save draining water off and takes about 1/2 hour.