Hot water OK but Rads cold

[PaddyBourne]

Have pumped system, mid-position valve and plenty of hot water.

As of weekend, no heat on radiators. valve positioning indicator moves to correct place when I select HW, CH or both, but dont get heat to radiator at any position.

Components are:
Drayton Lifestyle LP241 Controller
Drayton Lifestyle 679H340-30L0 three way valve - seems to be one that can't just have the motor removed.
Drayton HTS 3 Water Thermostat, tried turing to high with both HW and CH on, but still made no difference.

Grundfos Selectric 15-50 Pump - tried bleeding but lots of air - suspect coming from overflow.

I am assuming boiler OK as hot water fine. All Radiators have TRVs ( I am aware that one shouldn't) most downstairs are set full on, upstairs are mixed settings. Have bypass with handwheel valve between mid-valve input and return (currently set to open but was set to about 30% open).
Don't know if relevant but small rad in bathroom needs bleeding about once a fortnight.
Have tested that the thermostat gets mains and switches (in fact have bypassed it without result).

You might have noticed that I am trying to provide as much info as possible, having lurked here since Monday, and seen many posts which might have needed ESP to solve. Scarily many were still sorted

Any ideas?

 

[gas4you]

Is the boiler and pump coming on when ch is asked for? If no then sounds electrical fault with 3 port valve head. If yes then air lock, blockage or valve body problem.

In this case take valve head off whilst ch calling and try turning the shaft on the valve body. You could also do this whilst just hw calling then if rads get hot you have confirmed valve head fault.

If you suspect air lock firstly check exp tank in loft is full, then bleed all rads, close by-pass, turn heating on omly, pump full speed and all rads off except one, if this pushes air into rad bleed then move to next rad etc.

 

[Bambergaspipe]

Check your tank in loft isn`t empty.

 

[PaddyBourne]

Thanks for the info. None of the tanks in the loft are empty (all three of them - see my other post).

I have to admit to having had a fiddle and the following are further points which may (or not) shed light.

Every time I try to bleed the pump I seem to get air out of it, gurgling, plus drips, but never the "squirt" I get when bleeding the rads.

When I release the small bleed screw above the three way valve (between the valve and the cylinder hot pipe input) neither air nor water come out. I still get hot water from the tap though.

Will check the boiler comes on when CH demanded (only) but the pump is a bit difficult to tell if it is running.

I am reasonably confident with electrics, is there any way of checking with a multimeter in the "junction box" where the various controls are spliced together to determine what is being demanded. This is easily accessible.

I will also try the bleeding sequence suggested over the weekend.

If I need to remove the valve altogether, would you recommend the use of freezer spray (I can get a valve for £40) or is that the point where I get a plumber in?

Thanks for the help and taking the time.

Cheers

Paddy

 

[fumb]

You've fully opened the bypass?

With CH only selected do the pipes to the bypass get hot indicating both boiler and pump are running

Go round all the TRVs and close them. Fully open a single one (preferably closest to the 3 port valve) . Close the bypass it to see if that forces water through the single rad. If it does then close this TRV (stop CH FIRST!) and move to next rad. Repeat process

Then crack open the bypass again!

Are you sure there isn't a CH thermostat lurking somewhere?

Have a search back through recent posts from ChrisR. He has posted a simplified wiring diagram a couple of times recently
THere are various wiring diags HERE

As ever take great care when poking about in the wiring centre

 

[PaddyBourne]

Should I not have touched the bypass stopcock?

It was originally about 30% (two turns out of 6) open, I now have it fully open.

How should I (assuming I get the system fixed) dtermine what the correct setting is?

remembering that I have no rads without TRVs but the one in the hall (where the thermostat is) is always set fully open (max temp).

Because the bypass is so close to the valve and pump (about a foot from the valve and two feet from the pump) it is difficult to tell about hot water running through since everything gets hot quite quickly in that area (which is why I think the pump must be OK).

Would a picture help?

Paddy

 

[fumb]

Water will always take the path of least resistance

With the bypass fully open you've given it a choice of running round miles of 15mm pipe and all the rads OR about 1ft of pipe direct back to the boiler. I know which option I'd take

It does need to be open a little otherwise the boiler will not flow if all the TRVs close. Probably about where it was before would be a good start
Not being an actual plumber I don't honestly know how to set it exactly. I'd close all TRVs, close the bypass until the boiler starts to show signs of kettling then open it up a bit.

 

[Bambergaspipe]

Sounds like a blocked cold feed. Open a rad downstairs, (put a hose on the drainoff ) & observe the small tank in loft, if it does not empty, you have a blocked cold supply to your heating system.

 

[gas4you]

Agree with bamber, as no water coming out of vent above 3 port valve. Blockage will be where cold feed t's into heating pipe work.

 

[PaddyBourne]

If the pipe was blocked where you suggest (I will check it Saturday), would this mean that no additional water would get into the system when I last bled the bathroom radiator (at the weekend ).

Am I right in then saying that (possible leap of understanding here from me), ....................if this happened this would either cause:
a) an airlock if air could get in or
b) a lower pressure in the pipework which would actually suck in air when I bled the pump or the small bleed valve, hence the prolonged gurgling and nothing coming out of the valve?

Am I in danger of a "Eureka" moment here or have I completely misunderstood?

If it is blocked then what are the options for unblocking?

Paddy

 

[gas4you]

Usually just cut out pipe work around the t and replace. If the cold feed gate valve is just above this t then you could turn off the gate valve, undo bottom nut and clear blockage with a ong screwdriver or the like. This will only work if pipe is straight and will push crud into system though

 

[Bambergaspipe]

Usually just cut out pipe work around the t and replace. If the cold feed gate valve is just above this t then you could turn off the gate valve, undo bottom nut and clear blockage with a ong screwdriver or the like. This will only work if pipe is straight and will push crud into system though

Wrong. to stop this happening again, your system will need to be close coupled, a decent plumber will sort out your pipework, or a decent Heating Engineer

 

[PaddyBourne]

Sounds like a blocked cold feed. Open a rad downstairs, (put a hose on the drainoff ) & observe the small tank in loft, if it does not empty, you have a blocked cold supply to your heating system.

Did the above, opened rad downstairs, ran some water out of it from drain into garden and "expansion tank" in loft started to empty until ballcock kicked in. Held up ballcock briefly to watch the water level decrease continue then allowed to fill properly.

Hot water still working fine, still not got any heat on radiators. Will try the fumb experiment next then the electrical diagnosis in the junction box. Have turned the room CH thermostat up to max to ensure that this doesn't complicate things - I can hear it click on and off when I turn it past the ambient temperature, so I again assume it is OK.

Thanks for the suggestions. At least I am now less worried about draining the system to fit a new valve if it comes to that.

Paddy

 

[gas4you]

Well we've eliminated a cold feed blockage, a positive step.

next as previously advised, turn off hw, turn off all rads except one, close bypass, turn pumpon full speed and see if this will push air lock through. If so do each rad in turn until all work

have you followed my first reply about checking valve body etc?

 

[PaddyBourne]

Have taken plastic cover off the valve head but it appears to be the "older" version of the valve which doesnt allow the motor/electrics to be removed easily. This is fastened more permanently to the actual valve body rather than "clipped" on like the ones I have seen for sale as replacements.

These new ones seem to have a "clip" or push button which sits on the other side to the three way indicator (H.M.W).

I may well try to remove it as a near-future step once I have cleared some of the other possibles / diagnostics.

At the moment, the weather is being kind so the CH is not critical and I am wary of "breaking the valve properly" and ending up with no water either. Pretty sure that I would lose major brownie points for that.

Please don't think that I have ignored any of the suggestions, I am simply trying to get through them in as painless a manner as I can.

Thanks again for the advice, be back soon.

Paddy