Central heating issues

[Lucy]

Hi, ever since I turned off my hot water water to plumb in a new basin, I've had dramas with my central heating. I turned off both the stop-cocks in the airing cupboard... I'm now assuming one was for the hot water and the other was for the heating system. Now when I have both the hot water and heating scheduled to come on at the same time, two of my radiators don't get hot. I have to turn off the hot water, which sounds like it makes a pump kick in, then the other two get hot too. I have a Draton mid-point actuator and a Grundfos pump. Any clues about what's wrong would be greatfully received.

 

[SimonG]

Shouldn't have had any impact on your heating. Any pics of the airing cupboard and what you turned off?

 

[Lucy]

Unfortunately I don't have a camera until Christmas day lol, but it was two red taps. One of them had no effect on the hot water but the other did. I'm not sure if this may be linked to the issue or a separate problem but the lounge radiator (one of the two that doesn't heat up when the hot water's turned on) has been getting very slow at heating up, even when I turn the hot water off, and even then it is stone cold at the bottom. Tonight it's doing nothing at all, even at the top :-(

 

[SJB060685]

As above Lucy.
Are you saying you're turning off the HW at programmer to get last rads hot?
Are they upstairs rads or downstairs?

 

[Lucy]

Yes, I have to turn off the programmer.
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One is upstairs, and heats up really hot straight away when I turn off the HW. The other is downstairs and is very slow to heat up and doesn't heat well at all when it does get going. They're both the same side of the house and are the only two rads on that side of the house. All my other rads are on the other side of the house and are absolutely fine.

 

[SJB060685]

Were they ok before your basin install or always a problem?

 

[SimonG]

Did you re open the red handled valves fully? Does one just keep on spinning?

 

[SJB060685]

Did you re open the red handled valves fully? Does one just keep on spinning?

What you thinking Si, not enough water in system? That's one thought I had

 

[Lucy]

The lounge rad was always a bit slow to heat up but it's only since I put the basin in that I've had the problem with having to turn off the HW to get it to heat up. I'm wondering if I maybe need to flush out the radiator then balance the system. But it still leaves me with the problem with the HW. It's not really a major problem because I can always stick the HW on in the middle of the day for as bit while the heating's off, but I'd like to know why it's happening.
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Yes Simon, I've opened them both to the max and they both reach a point where they stop turning.

 

[SimonG]

What you thinking Si, not enough water in system? That's one thought I had

Aye, one was heating cold feed and the gate valves snapped closed.

 

[Lucy]

I don't know if this would have anything to do with it, but when I first moved in 2 summers ago, even though the heating was switched off, every time the hot water came on (as programmed), the heating would come on too. I had a plumber out to look at it and he said that the motorised valve was working fine but for some reason the hot water was back flowing into the heating system. He ended up putting a valve in one of the pipes under the floorboards just outside the airing cupboard. It's fine since then, until I messed with the stop-cocks.

 

[SJB060685]

What you were experiencing was reverse circulation, common in older systems. It arises when the HW and CH return are plumbed in together. Two ways to fix that, run independent HW and CH returns back to boiler, or alternatively put a non return valve in CH return which is what the plumber did.
Again I ask were these two rads problem childs before you fiddled, or just afterwards?
The gate valve you closed was just the cold feed to system, what you did shouldn't of had any affect.

 

[Lucy]

The one upstairs has never been a problem before. I had the plumber remove the one in the lounge last year so I could decorate. He put a new one on in the spring, and it was always a bit slow heating. I'm not sure if it is actually getting worse of if I am just noticing it now that it's getting colder.

 

[SJB060685]

Like Simon and I said just isolating the valve shouldn't affect it.
Couple things you can check.
1. Check level of water in header tank in loft for heating (smaller one of the two) I suspect it will be normal but will rule out not enough water in system.
2. Try bleeding the rads, again I suspect this isn't needed.
3. Like you said above the system should be balanced. You could shut down a couple of the rads you know are good and see if the water starts to circulate and heat up the problem rads.

 

[Lucy]

I've checked the header tank and that's fine. I tried bleeding the rads the other day, but water came out of the lounge one straight away so that seems fine. I did get some air out of one of the others but it made no difference to the lounge rad. I'll try shutting off a few of the other rads like you suggested when the heating comes on later. Thank you very much for your help / time

 

[John.g]

You might just post the details of your Grundfos pump, I know you havn,t changed it but it may be on a low setting and may just need changing. It may be like this one, attached.

 

[Lucy]

Yes, it looks very similar to that. It's a Grundfos Selectric 98.2657

It looks like this one.

 

[moonlight]

Is one of the valves a bypass? and now opened too much

 

[Lucy]

Ummm, I don't know. The one that didn't turn off the hot water is on the pipe that leads from the header tank into the hot water tank in the airing cupboard. The one that did turn it off is on a pipe that branches off from the pipe between the actuator and the pump (if that makes any sense at all)!

 

[John.g]

Ummm, I don't know. The one that didn't turn off the hot water is on the pipe that leads from the header tank into the hot water tank in the airing cupboard. The one that did turn it off is on a pipe that branches off from the pipe between the actuator and the pump (if that makes any sense at all)!

Yes, it looks very similar to that. It's a Grundfos Selectric 98.2657
View attachment 41971
It looks like this one.

(The white selector knob), if its on speed I, select it to speed II, if on speed II select speed III.

 

[SJB060685]

Ummm, I don't know. The one that didn't turn off the hot water is on the pipe that leads from the header tank into the hot water tank in the airing cupboard. The one that did turn it off is on a pipe that branches off from the pipe between the actuator and the pump (if that makes any sense at all)!

I'm confused by your post. "The one that did turn it off is on a pipe that branches off from the pipe between the actuator and pump" what are you saying that turned off? Surely not the feed to cylinder, it sounds like a bypass link or heat sink rad.

 

[Lucy]

Moonlight, I think you may have fixed my problem and saved me a fortune for a plumber's call out... I now have hot water on and the upstairs rad that wasn't coming on is now piping hot. Downstairs still isn't warming up yet so I'm thinking that might be a balancing issue? Thank you! And thank you everyone else for your suggestions and time. I now know how my central heating system works too :-D

 

[SJB060685]

So it was a bypass that was opened too much? That all adds up. The rad still not heating is almost certainly a balancing issue now. Do you know how to do that? There is a post on this forum describing it if not, just search balancing radiators in search bar

Edit: bypass should be opened about a quarter of a turn or so.

 

[Lucy]

I've never done it before but I've googled it so will give it a go It's also patchy when it does get going, so should I take it off and flush it out before I try balancing the system. I'm thinking, if there is sludge in it, balancing it might just end up pushing the sludge through the whole, system?

 

[moonlight]

Your system may be dirty, it might be something you should think about when you have plenty of time. Ideally power flushing, but you could put a chemical cleaner in the system. Isolate the water to the header tank clean out, drain some water from the system. Put cleaner directly into the feed pipework. Dont drop in the tank as the chemical is likely to sit below outlet. Refill system and run, depending which chemical you use read instructions.

 

[SJB060685]

I would get some sludge remover from a plumbers merchant or screwfix etc. Sentinel X400 or similar, add it to the feed and expansion tank and leave in for a week or two and then drain down, if it's only mild sludge build up then this will do, if its excessive then I suggest a proper power flush. After you're happy I would go ahead and balance the system, you could balance first and then add sludge remover, this added circulation might shift the sludge around but it's quite dense and usually doesn't budge too much if excessive.

PS. Sorry I didn't fathom out what you were getting at sooner. From your description I was picturing the bypass gate valve as a cold feed valve to system.

 

[Lucy]

Thank you, I'll do that I think I probably confused you because I got confused about what tap did what! I'm just pleased I haven't broken anything and have figured out what was going on!