Re: Central Heating problem - 2A fuse blowing in honeywell wiring box

[Andy Hall]

Hello,

> >I have a Honeywell wiring box into which all the components of my CH >system are wired. In the last couple of days the 2A fuse in this box >has blown (twice) and a 3A one also blew - obviously I have a problem. > >The pilot light is still on. There are no signs of leaks. Presumably >it could be any of the components but presumably likely to be the pump >or the motorised value.

Depending on what the boiler is, it could be a fault there as well - you don't say what the boiler is. Often the pilot light does not depend on an electrical supply to the boiler working.

>I have tightened all the wiring connections in case there was any >loose connections - there weren't.

Th other thing to look for is whether there are any places (and it could be anywhere on the system) where the insulation on a wire might have been nicked or possibly chafed by it going through a hole in metal without a rubber or plastic grommet. Boilers can be favourites for this if the installer was lazy.

>My problem is how do I check these components if I have no power to >test them?

The problem as well is that these are intermittent.

>Could I put a 3 pin plug on them and plug them into the mains?

You could for the pump, quite easily, and the motorised valve less easily. These have up to five wires connecting to the motor and an auxiliiary switch inside. You need to pick the motor wires. Either you can take the cover off of the valve head and trace the colours to the motor or look at the manufacturer's data sheet. One thing to watch with this is that you will be feeding the item under test from a different power source and this means that it is not isolated at the same time as the rest of the system if you switch that off.

I don't think that you would be able to diagnose much more than the pump and possibly the motorised valve this way. The boiler will typically have multiple connections and you really need to know what you are doing and have the manufacturer's service information .

One candidate for the fault you are describing is failed insulation and shorted turns on the motor of the pump or the valve. This can manifest itself as intermittent - I had a pump that failed that way once. FOr any of these tests, don't use more than a 3A fuse.

What could I put temporarily and safely across the fuse holder to keep >the system running for a while while I test it.

NOTHING other than the correctlhy rated fuse. The 2A and 3A fuses are there to protect the system and you. The 6 inch nail approach can result in more damage or even a fire so don't be tempted.

>Email replies to my address without the hotmail extension and >replacing the underscores with common email characters. > >If I got a circuit tester what checks could I carry out with or >without the power on?

On an intermittent fault, I don't think that you will see all that much.

>I do recall a plumber coming to my last house, putting a circuit >tester across the pump terminals and instantly telling me I needed a >new pump. But he of course had power.

It could have been a failure that was an open circuit, a short circuit or even an insulation breakdown to earth.

>Finally what would I expect an CH electrical engineer to charge me to >do the relevent checks (North London)?

You might want to look back through recent posts and find Ed Sirett. His email address is in his signature and is in North London.

>All help gratefully received. > >Charlie

.andy

To email, substitute .nospam with .gl

[Alan James]

I've had this twice and both times it was a failing synchron motor (not yet failed) in the zone valve. Might be an idea to get a spare synchron motor if you havn't got one. Were fairly cheap from BES, now you have to pay postage.

I would first check if you have separate mains feeds to boiler and wiring box. If separate I would not suspect boiler or pump initially. The intermittency may just be due to the actual current being drawn. Don't have the tables to hand but depending on the actual current the fuse may take some time to blow. If you are confident (and competent) I would suggest inserting a test meter on ac Amps in series with each load (zone valve(s), pump, boiler etc). Obligatory health warning - switch-off while connecting. What I might do in this situation is to fit a 13A plug (3A fuse) to the feed and plug into a 30mA RCD. Healthy readings should be nowhere near 3A. OK, won't work if it is genuinely an intermittent, but I would suspect not.

Cost of Plumber? Sorry d-i-y here, you can buy a lot of pumps, zone valves, test meters etc for the cost of a plumber.

Alan

[PoP]

You might need to post this in alt.geriatric.trainlovers ;)

PoP

[Charlie]

*********UPDATE*********

Had a bit of time today so this is what I did. Got a card of fuse wire

- cheaper than 50p a go fuses, even if a bit fiddly!! I turned off the power and replaced the fuse. I disconnected the red wire feed to the pump in the wiring box. I set the programmer to off for both CH and HW and turned the power back on. All ok so far. I then switched the programmer to call for HW, still ok. I then switched the programmer to also call for CH, still ok.

Eureka I'm thinking...it must be the pump - Grungfos 15-50. Based on a previous post I tried to get hold of a replacement capacitor but no luck. Decided I'll replace the pump, on the basis that even if it isn't the pump this time at least I'll have a replacement next time. I turned off the gate valves eitherside of the pump and tried to remove the pump. Unfortunately I didn't have large enough spanners to remove one side of the pump so reconnected to pipework again. What I didn't realise was that whilst I had the gate values on either side of the pump disconnected, the boiler couldn't come on. Presumably this means I have a fully pumped system?

Anyway I decided to leave the pump disconnected this evening and try again tomorrow. Bear in mind that at this time I'm still thinking its the pump. The boiler was on and happily heating water and approximately 40mins to an hour later the fuse went pop again.

When I was in the plumbers merchants he said if the pump was gone it would smell of burning - it doesn't.

So now where do I stand? Have I confirmed it ISN'T the pump? Does the fact that it took 40mins to an hour to blow indicate the blowout happened when the motorised valve was moving to a different position once the HW was heated?

Back to you boys ot there.

Charlie

And it was ok foabout 40minutes. The fuse then

[Charlie]

When I opened the inspection at the front of the pump I got quite a bit of water coming out of it, as opposed to a few drips. Is this normal or does it indicate a knackered pump?

I put a screw driver in to try and turn it but nothing. Didn't have a torch so unsure whether I was seating the screwdriver correctly.

Took the motorised valve apart - there is very little movement. when I turn the valve but about the same as the amount of movement in the motor. However when the motorised part was off and I slid the manual overide lever across to manual, I got a consistent amount of resistence and the lever comes back ALL the way to "Auto". But when the motor and valve are back together the lever can be moved over and back by about 1cm without any resistence. Is this normal?

And finally I opened the drain valve to drain the system and "NOTHING". There doesn't appear to be any water in the system. Presumably no water would cause overheating of the pump. Could this blow the 2A fuse in the wiring box or could other parts overheat?

Cheers

Charlie

[Andy Hall]

It could do, but doesn't correlate with your thinking the system is empty.

Are you sure it isn't the plug of th drain valve sticking? They do that sometimes.

If the system really is empty, the pump would not last very long.

.andy

To email, substitute .nospam with .gl

[Charlie]

False alarm - there is water in the system - must be an old drain c*ck.

Tried again today with the red wire feeding the pump switched out and the valve manually turned on but it blew. Valve obviously kicked in cos when I checked after the blow the vavle had retiurned to the auto position. Tried with the valve feeds all out also also blew. Did manage to get it going for a short while but then the boiler went out. Managed to restart the pilot ok.

I've given up!!!

Charlie

[Charlie]

Had the Electrician in. None of my components had gone!!! It turned out there is a break in the cable running from under the stairs to the kitchen. About 15 metres of cable nicely boxed and hidden. I did it myself around 15 years ago so I can't complain too much!!

Now my problem is do I run a new cable in some sticky back trunking along the skirting and behind the kitchen cupboards where it can be seen (concrete floors unfortunately) or do I try and pull a new cable thru the existing boxing which also contains the pipework? I previously used twin and earth lighting cable. Electrician suggested I use 4 core as a replacement as any future boiler is likely to have live in addition to switched live. Will the new cable be up to being pulled through about 15metres of boxing, 2 walls and 3 corners.

Cheers

Charlie

[stefek.zaba]

No to both questions, I'm afraid! For the first, it's not accepted practice to run mains-carrying cable in the same compartment as pipework, on grounds both of heat (presumably the pipework includes the boiler output - 70-80 degrees?) and of what-happens-if-there's-a- fault-exposing-conductors (like, we're pretty sure the pipework's earthed, but just *how* sure are we?)

For the second, pulling cable round three corners, expecially with other pipework in their, is pretty much doomed to failure; and likely even if you manage to damage the insulation.

But hey, maybe you can use this as an excuse to buy a nice new SDS drill so you can channel the 4-core neatly ;-)

Stefek

[Dave Liquorice]

Pipework as in CH pipes to from boiler? Ordinary PVC cable doesn't have a particulary high temperature rating. 80C+ from boiler pipework probably exceeds it. I don't think we need be concerned about heating from the load if you use 2.5mm.

If you can get clear straight runs you should be able to do it. No chance around a corner, let alone 3.