Draining and Recharging Queries

[MartyMalabu]

Hi

Can I start by saying I have read the FAQ on "Draining down you CH system", however I have a couple of further queries on this procedure and would be very grateful for any advice.

The background here is that even though I have replaced a faulty motor and a faulty uSwitch in the 3 port valve, I still only have hot water. The "CH Test" shows that the valve is not driving over when both wires are live, so I need to change the 3 port valve. I am happy about changing and wiring the valve, my lack of knowledge is in emptying and refilling the system.

1. There is an isolator in the circuit between the pump and the valve. If I wind this in will it help in avoiding airlocks, or, as I suspect is it more likely to cause problems in draining. Should I be to doing anything with this isolator or should I leave it alone?

2. I have an open vented system with a header tank in the attic. I have a litre of inhibitor. The property is a 4 bed new build with around 14 rads. Is this likely to be sufficient (the inhibitor bottle says it will do up to a 100l litre system)

3. Is there a procedure for adding the inhibitor. E.g., should I just tip it all in first when starting to refill the system, drip it in a bit at a time while it is filling, or do something else? Does it really matter.

4. What is the procedure for getting air out. I assume I start at the rads nearest the boiler and work outwords? Any other tips.

Many thanks.

 

[mysteryman]

The valve should give 'CH only' when the grey and white wires are live. The synchron motor will run the valve full travel, and the orange will be live to power up the boiler and pump. Check that the motor is OK. If there is 240 volts across the motor wires and it does not run, it has failed.

Many valves can have the motor or the complete head assembly changed without draining down. If it is a Honeywell valve older than about 25 years, this may not be so.

 

[MartyMalabu]

The motor I took out had no coupling between the motor shaft and the output cog, although the motor winding was not open circuit. I believe the new motor is OK.

 

[Whitespirit66]

1) No, leave this valve open, or it could prevent proper drain down. Also, make sure you slide the lever over on the motorised valve, and latch it so it stays over. This will aid draining down. When you put the new valve in, make sure the lever is also latched, then only release it when system is refilled.

2) Need 2 bottles. One bottle is good for approx 10 medium rads.

3) When system drained, you may have crud to clean out from your F&E loft tank. Just before you are ready to refill system, pour the bottles in bottom of empty (& clean) tank. Then fill system.

4) Bleed all rads, and pump (remove screw in middle of pump, and replace when water trickles out). Run system for half hour. Bleed again. Airlocks may occur, and take a while to work themselves out of system.

 

[MartyMalabu]

Many thanks for replying in such detail.

 

[MartyMalabu]

Changing the 3 port valve went really well so thanks for your help.

However, I now have another problem - which could have been there all along as the previous fault was that the 3 port valve would not give CH. The new valve works great in all three positions - However.

Once CH alone is selected, the boiler and pump continue to run ... forever. [Edit .. not quite forever, the boiler seems to cycle when it reaches its internal max temp] We used to have a freezing house, now it is the opposite. What can be causing this?

They continue to run even if the programmer is set not to call for HW or CH. I first suspected that the new valve might be providing 240v to the boiler/pump continually (somehow derived from 240v HWOff line). But if I disconnect the orange wire coming from the 3 port valve, the pump still has 240v across it and the boiler is still running. I.e. this is not being driven by the 3 port valve. If I switch the system off, and then back on, it does not seem to call for the boiler/pump; only once CH is called for.

System was fitted in a new property in 2002 and is as follows :
Vented Y plan
Glowworm Micron 60F boiler
Honeywell V4073 diverter VALVE V
Honeywell ST6400C Programmer

Any ideas please...