UNSUAL WAY TO TEST A DHW CIRCULATING PUMP?

[zappastix]

Hi

This is an odd request - but let me explain.

Alpha CB28 LPG Combination Boiler

The boiler has stopped working - no hot water and no central heating.

The fault finding page of manual point to two possible faults.

ONE

If the "B" light flashes every 5 seconds or so, and I think it said if you cannot hear the fan then it is either;

PC Board - test between MB36 and MB39 (I think its these numbers, haven't got manual here now).

Could find lots of MB's but not 36 or 39 (used a mirror and magnifying glass).

TWO

The circulating pump.

If the pump is not jammed replace the pump. The pump is not jammed it spins fine and semi clear water came out.

We have lived here 11 years and the pump has never been replaced. The boiler didn't seem that new when we moved
in so it's fairly old.

Around 20 years ago I had a pump go on me after 4 years after I installed a new boiler with lots of radiators, hot water
cylinder with immersion heater and motorised valves - best of both worlds - if either gas and/or electric is off, shower still
works - I loved that system with Aqualisa 60 foot head power shower pump.

Someone came out and checked everything I had done - didn't want to blow the house up on mains gas.

So it seems that sometimes pumps don't always last for long periods.

We had a service contract with British Gas for 3 years but stopped 2 years ago.

British Gas replaced a lot of things on the boiler including the heat exchanger AND I'm absolutely certain the PCB.

The PCB looks very new.

The fast blow fuse is okay.

On Friday I phoned as many Gas Safe engineers as I could, either they couldn't come out for over a week and
when they did arrive I'd have to wait for a pump to be ordered, if it turns out to be the pump
(I told them I thought it was).

On top of that, not one Gas Safe guy held the LPG ticket. So still couldn't come out.

We live on the South Coast, LPG is widely used, couldn't understand that local engineers wouldn't deal with LPG.

For medical reasons we need the shower up and running. We have an electric shower as well but that has problems.

So I had to make a decision, and have taken a chance and ordered a new pump on Friday for delivery on Monday.

Ordered: Grundfos UPS2 15-50/60 (130) A+ Eff. Domestic Heating Circulator 240V (replaces UPS 15-50 + UPS 15-60)

My old pump is a UPS 15-60 (130) so I'm hoping it will be okay.

~~~~~~~~~~~~~~~~~~~~
OK HERE IS MY ODD QUESTION
~~~~~~~~~~~~~~~~~~~~

Before I fit this new pump and scrape all the "red paint off the threads" I would like to see if it is
the pump that is stopping the boiler from firing up.

So do you think the following would work?

I leave the old pump exactly where it is i.e. with pipe work still connected BUT I disconnect electrics from OLD pump
and connect cable to NEW pump.

Holding the pump in my hand or rig up a platform for pump to sit on, when ready start to pour water into pump while my
wife "flicks" power on at wall switch ON/OFF very quickly so that I can feel if the pump starts to vibrate.

I would pour water in to pump so it doesn't burn out although I only need about a 'second or so' to know if it's going to work.

Of course I'd make sure that no water can reach any electrics and PCB board.

If I cannot feel the pump vibrate then I'll send the pump back and swallow the return postage.

Do you think this is OK?

We want to get a new boiler but this was next year, so don't really want to waste money on a pump if not needed.

I would treat the new pump while testing extremely carefully including leaving no marks on electric screw points, and
thoroughly dry it out.

Mad idea or what.

Just one other quick point- is there a way to "drain just the boiler" without draining the whole central heating system?

Any ideas or help appreciated.

Many thanks.

Stephen

 

[45yearsagasman]

Have you tested anything using a multimeter and following the fault finding chart? Power to the pump etc?

 

[Nozzle]

Rather than knacker up the pump trying to test it when not primed, why don't you just use a multimeter to see if there are volts at the terminal..

Nozzle

 

[kidgreen61]

Can't you just connect a flying lead to the old pump to see if it works?

 

[petit_pablo]

FML

You need to get hold of a multimeter and test it properly.

 

[zappastix]

Thanks everyone.

I have got a multimeter somewhere (finding it is a different matter), I did mean to learn how to use it but never did. It had so many numbers on it and no helpful instructions I didn't use it for what I brought it for.

I think I best try "kidgreen61" suggestion, using a 3 amp fused plug as a fly lead direct to pump (after disconnection at pump side from PCB).

If the old pump works then it will be a new PCB (that is what fault finder says).

At first I thought it might be the fan, that went on us one Christmas morning about 8 years ago (that I replaced myself), but the fault finder doesn't touch on that.

Thanks.

 

[muggles]

At first I thought it might be the fan, that went on us one Christmas morning about 8 years ago (that I replaced myself)

Did you use a flue gas analyser after you'd replaced it to ensure that the boiler was burning correctly, or did you just assume that it was "because it looked/sounded OK"?

 

[Justin Passing]

It may well not be the pump or the pcb.

EG, Pumps runs

1) water flows: unless there's some blockage, perhaps built up boiler scale. It has to flow enough such that

2) boiler detects water is flowing: unless the detection mechanism is faulty, or the detection switch is faulty

3) the signal has to arrive at the pcb.

OK, you're missing some important detail about how it works, and you aren't experienced with a meter.
It's a potentially dangerous appliance where you could miss something else and waste money or do damage, to either it or yourself.
It might be better to wait, inconvenient though that may be.

 

[zappastix]

Hi

First chance to get back and wrap this post up.

Just thought I'd add what the final outcome is going to be for those
that have followed other posts connected to this one - purely to help
anyone else who might find themselves in a similar situation.

I have included this post to the others posts connected.

I looked in to other boilers that others recommended.

I also checked other web sites with Boiler Installers recommendations
who on balance rated Worcester Bosch Greenstar **CDi Classic
as the boiler to go with.

Briefly a while back I did a flow rate test - 10 seconds gave me two litres.

So this equated to 12 litres per minute.

The boiler to be replaced was an Alpha 28CB.
The 12 litres per minute would have matched the Alpha.

I nearly went for Greenstar 29CDi Classic LPG - because that was the nearest
to the Alpha . . . . BUT I thought I best double check flow rate again.

This time I did a FULL 60 SECONDS and this resulted in exactly 14 litres per minute.

I really don't understand this discrepancy, (12 vs 14) but this is what it came out as.

So I phoned Worcester Bosch main help line - the woman didn't have a clue what I was asking
about and put me through to Technical dept.

The guy said the two boilers that I thought would be okay the
Greenstar 34CDi Classic OR Greenstar 38CDi Classic were both okay with 14/lpm

He said he'd go for the "38CDi" because it delivers 14 litres per minutes at 40 degrees.

And because it's not more than around £150 I'm going to go for the Greenstar 38CDi Classic LPG

I asked about an installer, he said if you use a local Gas Safe guy I wouldn't receive 7 years
(8 with fitted filter) parts & labour guarantee BUT I would get 5 years parts & labour guarantee.


For those interested Greenstar info;

Greenstar 34CDi Classic

Central heating output: 30kW
Domestic hot water flow rate: 14.3 litres per minute at 35 degree temperature rise
(provided adequate mains pressure is available)
Designed operational flow rate 12 litres per minutes at 40 degree temperature rise.


Greenstar 38CDi Classic

Central heating output: 30kW
Domestic hot water flow rate: 16.4 litres per minute at 35 degree temperature rise
(provided adequate mains pressure is available)
Designed operational flow rate 14 litres per minutes at 40 degree temperature rise.

Many thanks again - I couldn't have got here eventually without helpful snippets here and there.

Stephen

 

[pallen5000]

At first I thought it might be the fan, that went on us one Christmas morning about 8 years ago (that I replaced myself)

Did you use a flue gas analyser after you'd replaced it to ensure that the boiler was burning correctly, or did you just assume that it was "because it looked/sounded OK"?

Don't think I would of been using an fga 8 years ago on a CB24. It's not compulsory.

 

[mcmoby69]

Don't think I would of been using an fga 8 years ago on a CB24. It's not compulsory.

might not have been compulsory, but being competent would be a start!