CH temper mental

[Mr. Tickle]

Felix,

I presumed that when i was tapping the valve that i was releasing a mechanical, rather than electrical, problem. Surely if it's the same run of cable then i will be able to record a voltage drop at either end?

Are we talking:

It should be 240V.
The valve is not opening fully, so there are (i.e.) 150v going to it.

Or

Should it be 240v and it's 0v?

I'm not quite sure how it could regulate the amount of voltage using just a SPST type switch, or am I missing something? Is there a pot on the line that adjusts the voltage?

Would now be a good point to get a plumber in and point them towards the gas valve with all the evidence i've collected?

I have a spreadsheet with: Time, Prog Status, Pipe Temp, Room Therm Status, Room Temp, Tank Therm Status, Tank Temp, Valve Status, Gas Flow (ft3/min) and 'Effect' columns and have been filling it in.

Is that, along with this thread a good thing to give a plumber, or are they going to insist on going through the whole thing themselves?

Thanks again people.

Mr. Tickle.

Mr. Tickle.

 

[felix]

The 240 volts will reach the boiler just fine but you can lose some or all of it across a bad joint at the boiler end. Of course this is only a theory and the problem may indeed be mechanical failure inside the valve. If it was my boiler I would find a way in to the terminals and make sure they were all good connections. Then I would measure the voltages as well, just to make sure. Only after that would I condemn the gas valve.

On the other hand, I can understand your reluctance to go digging into the depths of your boiler. As Chris Tarrant might say, they're only easy if you know them. I'm prepared to tangle with most electrical or mechanical devices but if I found a UXB at the bottom of the garden I'd send for an expert. At least if you do get somebody in you can give them a lot of information and, hopefully, point them straight at the fault.

 

[Mr. Tickle]

Yea, that's what I'm thinking.

I presume you mean ordinance rather than the rock band?

I'd be inclined to pop a few .22's at it from my bedroom window first.

But there we go.

I'm more worried about prodding around not knowing what I'm looking for and you're right, They're Easy If You Know Em.

It's in me to have a poke around so I guess I have to start somewhere - I shall go through the manual.

I've phoned around today looking for someone to come out and have a look at it but no luck. I've been through the Yell pages and no-one is around for weeks.

Perhaps I can find out why this only happens in the week and duplicate our weekend settings.

Thanks again for your input, Felix. It's much appreciated.

Mr. Tickle.

 

[MANDATE]

The gas valve will operate using a electrical solinoid so you should have live in and neutral out, or there could be 2 solinoids controlling two internal valves so you would have two live inputs and a common neutral. One of the two valves is used in conjunction with electronic ignition to light a pilot light which in turn lights the main burner when the second solinoid operates. No doubt the wires will be tracable to a socket attached to the valve, which will need to be removed to get access to check voltage.
Hope it gives you some idea what you're looking for.

 

[Mr. Tickle]

Yes, that does help to be honest.

The heating works every time if I turn everything off, then back on an hour later. The rads are bouncing off the walls!

I tried to set the programmer to run a HW cycle, then turn off for an hour, then turn CH on - but both HW + CH came on. I can't have one or the other!!!?

Is this the programmers fault or is it the way the physical plumbing is laid out?

If it is the prog, i could fit a new one and this problem would go away. I'd be happy to live with it until the boiler needs servicing/touching up.

Thanks for your helps guys and gals. I will open it up tonight and let you know what happens!

Mr. Tickle.

 

[felix]

I've just reread the whole thread and spotted something that I'd forgotten all about.

"Just come in from work - rads are cold again. The therms etc. are all open. I have moved the valve over manually to MAN and the boiler/pump started up."

You also indicated elsewhere that, although it doesn't always do this, it has happened this way before.

Then there's the oddity of being unable to get CH only, even though you've had it before. Remember how the valve went right over by itself and the boiler started? That was CH only.

It's possible that you have two separate faults. To get CH only, your controller must deliver a healthy No-HW voltage to the valve. That's what it takes to drive the thing right over. The lack of HW is not enough to do this. Rather confusingly, when the valve DOES go right over, HW will reappear but it's coming FROM THE VALVE not the controller.

Just to add to the confusion, if the controller is calling for HW but the tank stat says no, the HW voltage from the controller is switched away from the boiler and onto the No-HW wire - or is it? A fault in your tank stat could leave you without either of these voltages.

Here are a couple of possibilities worth considering:

1) CH and HW are on at the controller but the tank is already hot (you've been out all day) so the tank stat overrides the controller and says No-HW - except that it doesn't! The CH demand has driven the valve to mid-position but, with no HW demand, the boiler stays off. You push the valve right over, it's internal switch feeds the CH demand through to the boiler and it starts up. Unfortunately, with no proper No-HW voltage to hold it there, the valve drops back and the boiler goes off.

2) There may be something significant about the fact that things work for one hour. This is typical of how long Boost will run on a controller. Perhaps your controller is (intermittently) faulty. If it's putting out insufficient voltage your gas valve might not open properly. With modern electronic controllers it's perfectly possible to get only alternate half cycles of mains voltage coming out (I won't bore you with the details right now). I'm not sure how this would affect a gas valve but it certainly dims a light bulb.

It's time for the multi-meter if you feel up to it. These particular faults CAN be found by measuring in the connection box. There will be wires to both stats, the valve and the boiler and one bringing power in, usually but not always from a fused connection unit. Since you're clearly not an expert on electrics and you'll be working near lots of earthed water pipes, remember the hand in the pocket rule - redoubled in no trumps.

PS: Strictly speaking, it's against the law to take pot shots at rock bands!

 

[ChrisR]

Can you find a boiler identity anywhere - the rating plate perhaps will have the GC (Gas Council) number? Sorry if you've answered this and I've missed it! From that we could be looking at the right Mfrs Instructions!

I would definitely, somehow, measure :
the voltage ot the gas valve, when it's doing its simmering thing,
the voltage at the Switched Live input to the boiler, when it's supposed to be ON.

Without those the fault(s) still could be the motorised valve, the boiler's pcb/electronics, or the gas valve.

 

[Mr. Tickle]

Phew, this is getting long!

I'm going to print this out and file it next to my Britannica volumes!

Anyway - what i meant by 'working for an hour' is that the heat appears to come into the rads and then after about an hour, it gets cold. From what I can gather - the boiler is never heating the CH system during that hour and it is just the heat from the HW tank running through the system.

I presume this as I have observed the tank temp drop slowly over that hour, gaining speed in its decent towards the end of the 60mins.

This may point to the valve not working or another problem, or I could be wrong.

There are some neon lights on the circuit board, apparently, which can be used to diagnose faults. This, again I presume, is the orange glow i could see under the boiler, behind the control box.

I am going to go through this entire thread again and highlight all the electrical suggestions then go at it this weekend.

Even if I don't find a fault, i'll have learnt more about the boiler and I'll be able to find a fault later on.

We use a lot of 3phase 520v stuff at work and I'm happy as larry to replace fuses and add connections - as I know the basic rule of precaution -

If you don't know 100%, DON'T.

I've had enough 240 shocks in my life as a youngster who's brother took everything apart and left it that way, to know, basically, not to.

There are some good detailed fault finding flowcharts in the manual and now on closer inspection, they even tell you what voltages should be between which terminals. So you've all given me the confidence to have a crack at it - which is what this is about really.

Mr. Tickle.

 

[MANDATE]

Mr T, This is not intended to solve your problem, but you may learn something from it. My sons heating system was mis behaving and he thought the room stat must be faulty. However I went to show him how to test it and could not find any fault. At this stage I did not know the precise operation of the 3 port valve, but within a day or so I had all the necessary information. On the next visit we tried HW only and the boiler performed perfectly with the cylinder stat functioning ok. Then we tried CH only and the boiler failed to function. Then we tried HW and CH together and again boiler failed to function, it occurred to us that the HW was already satisfied so we ran a little hot water off which triggered the stat and boiler flashed up and the radiators also got hot but not for long.So we could have heating but only when there was a demand for hot water. Now the hot water was not in constant use so most of the time no heating.A test of the 3 port valve showed it was moving from mid position to CH position but it also triggers a couple of micro switches as it passes mid point, one of which supplies voltage out of the valves orange wire. A test showed we had no voltage on this orange wire (tested in the junction box) The test included the white wire and the grey wire as the valve rested in the three different positions. The conclusion was that the micro switch had failed.
A new actuator head was fitted and problem solved. The old head was dismantled and micro switches tested. 1 ok and 1 failed. Failed switch was de-soldered and opened up, contacts found to be dirty but not burned away. After cleaning the head was re-assembled and switch worked ok. Next a simple test rig in the garage. 2 way switch to represent HW part of programmer. (HW ON and HW OFF)1 way switch to represent CH part of programmer(CH ON/OFF)1 way switch to represent room stat. 2way switch to represent cylinder stat. Bulb holder and bulb to represent boiler.
All wired up correctly and functioning ok in all modes.

 

[felix]

OK, we drop the controller boost theory. For some reason as yet unknown, your boiler is dropping back to simmer. The pump still runs and sends boiler water through both cylinder coil and radiators. The stuff coming back from the radiators has lost heat but on each trip it is re-mixed with stuff coming back from the cylinder. As the water temperature drops, the cylinder coil begins to suck heat OUT of the cylinder water. This is exactly what you are observing.

That leaves two questions unanswered:

1) Why is the boiler dropping down to simmer? It never seems to do this when you have a hot water demand (controller AND tank stat) which seems to let the gas valve of the hook (great relief all round).

2) Why does the boiler start up when you push the valve from mid position over to CH only?

I can see one possible answer to the second problem. You are losing No-HW, either at the controller or in the tank stat. With both CH and HW demanded, the CH demand drives the valve to mid position while the HW demand powers the boiler. If HW goes off and No-HW does not replace it, the valve stays put but the boiler goes off. When you push the valve over - as No-HW should have done - you close a switch inside which routes power from CH demand back to HW demand and from there to the boiler. Unfortunately, without No-HW to hold it, the valve drops back and the boiler goes off.

I can also see another answer. The valve sometimes sticks. No-HW tries to drive it to the end but fails. In this case, once you push the valve over it will stay there.

I have as yet no answers to the simmering boiler problem.

 

[croydoncorgi]

SURELY by this time it would make sense to Get Someone In???

 

[Mr. Tickle]

Well, the reason that hasn't happened is that of the 7 plumbers i've called/already had in, non of them sounded like they had a clue. Most didn't beleive it was acting as i said.

I've called around and no one is now available for weeks.

So i'm trying to get all the evidence i can, diagnose it and hopefully be able to point a competent engineer straight at the problem.

I've asked a house-builder mate of mine and he said 'oooh, in my day, you'd just throw in a new thermocouple - these days 'dem dare boilers are ahl elastic trickery. Engineers come in with their probes and fiddle about.'

Well, i thought that if no one can come in to do it, and I have the manual that shows you how to do it and the tools to do it. I kinda figure I should.

I would much prefer to make a phone call and have a guy come round and sort it - but it aint that easy. I haven't been able to duplicate the problem whenever I want - people come in, turn everything on/open and it works. No problems. Call out charge.

The other half of me says - as a new homeowner, i should really take an deeper interest in how things work. My DIY isn't that bad and if someone came in, I'd only want to watch them working.

I understand your point CroydonCorgi and I also appreciate all your help that you've offered in this thread.

Cheers,

Mr. Tickle.

 

[Mr. Tickle]

A plumber that came in said we had to have HW and CH at the same time, because of the way it was setup.

Did he mean the way the pipes are or is he talking about the controller?

Is there some reason why they physical layout of the pipes would stop us having just CH if we needed it?

Is it just the programmer that is stopping us doing this?

I have a Danfoss CP15 but can't find a manual for it online.

Can someone tell me about the layout of the piping? It;s a Y-plan.

Perhaps there is something i should look for that would tell me about the CH+HW thing?

If it is the programmer stopping this, i'm going to go get a new one this afternoon.

Mr. Tickle.

 

[felix]

Your pipework is perfectly capable of giving you CH only. If your controller has a wire coming out of it which is live ONLY when there is no demand for HW then it is also capable of giving you CH only. To make it work you must have it wired up right and two switches in the valve must work.

More precisely, the No-HW demand from the controller MUST get to the valve and then THROUGH AN INTERNAL SWITCH to drive the valve from mid position to the CH only end. At this point the CH demand going to the valve MUST be switched out again (lots of people on this forum are saying it's the orange wire) and this MUST then be connected by some route to the boiler gas valve. You need to do some measuring.

I can see just one other way in which the system might fail. It was mentioned a while back that your boiler might cut out (or maybe go into simmer mode!) if it sensed insufficient flow rate. If your radiators have TRV's the flow rate will drop right down as the rooms warm up. Of course the flow will come back when things get cold and I would then expect the boiler to restart but who knows. You might have to turn it off and on again.

If you do suspect a flow rate problem try opening your bypass valve a bit more. You should find it somewhere near the boiler and pump. It'll probably be in a run of 15mm pipe and if you follow this you'll see that it allows water to flow through the boiler and pump ONLY, bypassing the rest of the system.

 

[Mr. Tickle]

We don't have TRV's fitted.

I have found the bypass - i'll do the measurements on the boiler first.

Last night, it didn't work - so i turned everything off at the programmer. Usually, we leave it for an hour and turn it back on again. This time i turned the proggy on after 10mins - everything fired up + rads bounced off the walls all night.

This is getting really really interesting now. I'm of the ilk that i personally should find the problem now. I'm hooked.

Is this a bloke thing? Is this how those 'DIY disaster' programmes get their fodder?

Well, I'll have a poke this weekend and see what i can see.

Mr. Tickle.