Partial CH following Water heating.

[robcol1305]

Our boiler heats both the Central Heating and hot water tank. The timer is set to operate them at separate times; generally the CH is set to come on early morning and then the evening. The hot water is set to come on late PM ready for showers the next morning.

We have found if there is a demand for both simultaneously, then the CH works ok but the Water does not heat and hence we’ve set the timer to operate them separately.

Our problem is that if we boost the hot water, say during the day, and that completes, then flick it back to CH, only the upstairs bedroom radiators heat up. **The upstairs bathroom and ALL the downstairs radiators remain cold**

With only the upstairs bedroom radiators coming on, the flow circulating soon gets too hot for the boiler’s internal thermostat and so it turns off (as it should). The boiler comes back on after a short time, but the flow still only circulates around the bedroom radiators.

In order to get the flow circulating back to ALL radiators, I have found if I turn off the heating demand for 40 minutes, I can then flick on the CH and then all radiators heat up as normal.

I thought it must be some upstairs valve/switch getting hot which then stops the flow to the downstairs, however on the odd occasion, when the CH demand comes on in the morning, only the three bedroom radiators heat up, despite the hot water demand not having been on since the night before, albeit the Water was the last thing to operate.

All radiators work a majority of the time, balancing seems ok and I can hear the pump working all the time there’s demand.
(I am not a heating engineer so limited on testing I can carry out.)

 

[mysteryman]

Sounds like an intermittent diverter valve or 2 port valve fault, or perhaps a pump problem. It would be useful to know what kit you have.

 

[robcol1305]

I can get the Pump and Valve makes. What other kit would help.

 

[D_Hailsham]

I can get the Pump and Valve makes. What other kit would help.

1. How many motorized valves and which type (left or right pic)

View media item 5946 View media item 11762
2. Cylinder stat?

View media item 10596
3. Boiler make and model

4. Timer make and model

 

[robcol1305]

Boiler (Oil) - New June 2008
Trianco Contractor 50/70 WM HE

Pump - New June 2008
Grundfos UPS 15-50 130

1 Valve - New June 2008
Honeywell V4073A Mid-Position Valve

Timer
Horstmann CentuarPlus C21

Cylinder Thermostat
Landis & Gyr (no model number)

Room thermostat
Honeywell T66200B1008 (Digital)

 

[nelectric]

Sounds like there may be a blockage in the valve, or the control head (the silvery box on top of the valve) is malfunctioning.
Are you wanting to get your hands dirty and fix it yourself, or are you just after a pointer as to what is wrong, then you will get a professional in to do the work?

 

[robcol1305]

When DIY involves Electric AND Water......it’s probably best for me to leave well alone!

Logically, it does sound very much like the Valve is a little temperamental?

When I was checking the make/model last night, I noticed the valve was reasonably warm. There had been no Water or CH demand on the system for the previous 20 hours.

Could someone confirm:-
When the Valve is pulled over by the spring, the Hot Water port is open?
When an Electric current is passed through, the Valve is pulled over to open the CH port?
With an Electric current passing through, the Valve would feel warm?

Thanks

 

[robcol1305]

Hi. Really appreciate some guidance on these questions.

Could someone confirm:-
When the Valve is pulled over by the spring, the Hot Water port is open?
When an Electric current is passed through, the Valve is pulled over to open the CH port?
With an Electric current passing through, the Valve would feel warm?

 

[nelectric]

This is a mid-port valve and so has three positions
HW only
HW & CH
CH only

There is always power in at least one or two wires to the control head, and the motor within it is constantly energised, no matter which of the three positions the valve is at. This is why it is normally warm to the touch, and that is nothing to worry about.

The 'normal' position for the valve is HW only. When the CH is activated the lever on the end of the control head should be floppy and very easy to move. When the CH is off there will be a lot of resistance to this lever moving, and when you do move it you will hear the gears inside whirring. This lever is used to latch the valve in the HW&CH position, either for servicing or to manually allow the radiators to warm up.

There are two common problems with these valves.
1. the motor inside the control head burns out. If this happens your CH will not come on and the boiler will not fire when the programmer or thermostat tells it to come on. This is cheap to fix - about £10 to buy a new motor, up to £25 for an official Honeywell motor.
2. The valve itself is not working because a). there is debris stopping it closing or opening properly, or b) the rubber ball (which IS the valve) has perished or become hard. To change this, the parts are approx £15 and the work involves draining down the system.

Either way is relatively cheap to fix yourself if you are a confident DIYer, otherwise I suggest you get in a professional who will do it quickly and efficiently. Be prepared to spend more on the parts though doing it this way.

 

[robcol1305]

Ok so we've limped on over the past x months with this issue, in fact it has got worse. I'm tempted to sell the house but the wife reminds me it would cost more, plus dealing with Estate agents/Solicitors would be far less fun.
So quick update……The water demand comes on, it runs for 15-20 minutes before you can hear an audible hi-pitch whine from the pump(?) and then the boiler thermostat cuts in as the water is not fully circulating. I turn off the demand, you hear a gurgle from the pump/valve and then you turn it back on and it may be fine, or you may have to do this two or three times before the whine disappears.

We’ve had numerous visits from the Heating engineer and various work to resolve this intermittent circulation issue. i.e. Alterations made to the feed pipe as we found it was running over; we then had a new pump; then a new diverter valve; and now we've just had the system power flushed (which including a two week period running with a sludge additive).
So you can imagine my disappointment (under statement) that the issue still persists.

It still appears to be a problem with an air lock; you can hear the bubbles passing through especially when it’s the demand for heating water. I don’t know if it could be the boiler itself introducing the air as if I run the pump without the boiler running (boiler thermostat set on low/off) the water circulation is very quiet.

Does anyone have any experience/advice to offer? Or more unlikely, know of a nice estate agent!