Possible 3 way valve problem - need confirmation if poss

[pjdavies2000]

Hi all,
First time poster, but long time reader of this forum.

Our central heating system has been messing about for a long time, so last weekend I decided I needed to get it sorted. I'll list what I did and results, and show where I have ended up, but first the equipment!

Bolier - Potterton Suprema 80
Radiators - 8 (4 up 4 down)
System - gravity fed with a Grundfos Selectric UPS 15/50 pump
3 port Valve - Honeywell V4073A (I am pretty sure it is this model, the valve is badly positioned in the airing cupboard so it may be wrong - sorry in advance!)

What has been the problem:
The boiler had a new PCB put in just before Xmas (apparently not uncommon with this boiler) and fired up fine with the hotwater (and I assumed radiators). However, alot of the radiators didn't seem to work. I then bled all the radiators (in the bottom up method) and still not heating to the radiators downstairs or one small one upstairs.

I then decided that it might be sludge through inactivity and the system being a good few years old. So I drained the system (much black water - although not 'sludge' removed), added some Fernox cleaner to the header tank and refilled the system, bled etc. However, still no hot water.
The radiators closest to the bloiler (bathroom, and 2 closest bedrooms) still got hot when hot water was needed (I know this as I could only get these rads to run if the hot water was running - so emptying the tank, and calling for more hot water.)

I drained the system again (to remove the fernox the next day, thinking this might need removing) but didn't add inhibitor as I didn't want to 'pour money down the drain' until i knew I wouldn't be flushing the system again! Still no joy.

I then did some checking on here, and found out all I could on the 3 port valve. (after I thought it might be the pump, but this works fine when being called on to be used).

I located the valve, and found a lever under it (it is really poorly positined, the lever is underneath, and very close to shelving etc), and managed to get it pegged in the manual override position. The pump started to move hot water into the central heating system - so at present I have upstaris, 3 rads working well, downstairs 1 rad working fully, 2 rads working, but suggestive of more sludge! and 1 not working at all - this one, the kitchen, the feed pipe gets warm to about halfway then goes cold.

For the two rads not working, I am assuming this may be partly to do with me needing to rebalance those rads. I can't work out fully what the piping network is, but is it possible that one system might run:
bedroom - livingroom - downstairs hallway - smaller bedroom - return
the other systems seem to be Bathroom - bedroom - kitchen - return and a single rad on its own loop in the downstairs WC.

The issue I have now, is that the boiler still only fires when it needs hot water - so not calling for rads at all, and as the valve is open, is sharing the hot water between the two (is this why some rads are not working, as the sharing of the water is reducing the effectiveness of the pump?).

Since have been at the house, we have always had to have both hotwater and CH running on the boiler controls to get both, although hotwater alone without rads will work as well, but ch by itself would never fire anything up - I assumed this was just how the system was built - what the boiler limitations were.

If I replace the actuator in the valve will this be the solution to my ch woes (I know I'll still need to do a sludge flush with cleaner and add inhibitor) or do you think there is more I need to look for before I run with this soultion.

Thanks for your help and advice in advance, and sorry for the lengthy post!
Peter

 

[D_Hailsham]

the boiler still only fires when it needs hot water

There are two causes for this problem: Faulty actuator or faulty wiring.

You can check the wiring if you have a multimeter set to AC volts.

Turn HW OFF and Heating ON at the programmer
Set the room stat high.
Measure voltage between Honeywell white wire and neutral; it should be 240v.
Measure voltage between Honeywell grey wire and neutral; it should be 240v.
Turn HW ON at programmer and turn HW stat down.
Measure voltage between Honeywell grey wire and neutral; it should be 240v.

If the voltage on the grey wire is not240v in both cases, there is a wiring fault. Check that there is a wire from the hot water thermostat to the valve grey wire, Also check that there is a wire from the HW OFF terminal of the programmer to the grey valve wire.

If the voltages are OK, then either the actuator is faulty or the valve is sticking.

Remove the actuator to expose the valve spindle. This should rotate easily over about 20° between HW open and heating open. If it is binding a little WD40 should help.

If the spindle is free, the actuator is faulty and should be replaced.


The other faults could be either sludge or balancing. Cleaning solution needs to be left in the system for more than a day for it to work. Use Sentinel X400 and leave it in for at least two weeks. After a week, shut off all rads but one (open both valves on that rad) so the solution just passes though that rad for 15 minutes or so. If you have a rubber hammer, thump the rad to loosen any sludge. Then shut that rad and move on to the next. (PS make a note of lockshield settings so you can reset them at the end)

When you drain the cleaner, run water thought the system until it is clear.

If that does not solve the heat distribution problem, the system needs balancing. See Balancing Procedure

 

[pjdavies2000]

Thanks alot for this!

I hadn't even considered the wiring may be at fault!

I'm going to have to wait til the weekend, and have a go at it - my father in law is a sparky, so he'll have the equip to do the testing for me, and your guidance will let him know what to look for!

In the mean time I've set the whole rig up as per the guidance on here to run the boiler on low and the tank on high, so hopefully that will keep us nice and warm for the time being - and I can pump through some more cleaner!

Cheers again!

Peter

if anyone else wants to add to this then more than welcome.

 

[pjdavies2000]

just an update - since running the boiler and tank on the low-high set up all the rads are working fine, and I returned home last night to a nice sauna styled house!

I'm still gonna run some cleaner through and replace with inhibitor in a few weeks as per suggestion, and do the electrical tests over the weekend, and will update again as things move (hopefully) foreward.

cheers again

Peter