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Possible faulty PHE Sensor - Please help!

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Post  PeteMccarthy Mon Dec 31, 2012 6:33 am

Hi,

First of all thanks for running such a helpful site.

I've got a Pulsacoil 3 and had problems since I moved into my flat with only enough hot water for 1 shower. The boost switch had been left on permanently for months until I found this site and realised how it worked.

Since then I've drained the store and changed both immersion heaters (refilling with some Sentinel 100). The store heats up overnight and with the boost (the F&E tank is very hot to touch) but the water from the bath tap is lukewarm and lasts only minutes before going cold. Strangely the kitchen tap is considerably hotter but again only lasts for a few minutes.

I've checked the pump voltage on the PCB (with hot taps on) and I'm getting around 220v. The PCB looks fine (ie nothing appears burnt out). The light flashes twice a second normally and then 7 times a second when the hot taps are on. From reading this site the only thing I think it can be is the PHE sensor, DHW sensor or the mixing valve. What does this problem sound like to you?

To avoid ordering the wrong/unnecessary component can I check the sensors beforehand with a multimeter? If so, how? And if they are at fault should you change both of them and how difficult is it?

I'm willing to try most things myself and need to save money! Thanks so much.

Pete

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Post  mike Wed Jan 02, 2013 2:03 am

There is no way of checking the sensors.
I advise you read pages 13 and 14 of the manual.
Try running your bath tap slower and see if it matches your kitchen hot tap.
I assume the flow rate is ok?
Have you felt the mixer valve before it is mixed?
There is no easy fix and more so when not in front of the unit.
What age is the unit?
Mike
MGC/H2O
Norfolk

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Post  PeteMccarthy Wed Jan 02, 2013 2:28 am

Hi Mike,

Thanks for the reply.

Flow rate is fine. I will check the mixer valve before I mix/run bath tap slower and will repost.

The unit is approx 10 years old.

Thanks
Pete

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Post  mike Wed Jan 02, 2013 3:27 am

You really want to check the mixer valve by running the hot water.
If the valve is hot one side and cold the other?
And also check the PHE the same way!
Mike
MGC/H2O
Norfolk

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Post  PeteMccarthy Wed Jan 02, 2013 8:06 am

Thanks again Mike.

The hot pipe/PHE sensor attached are barely warm until I turn the hot tap on after which the pipe and sensor get very hot. The outgoing pipe is significantly cooler. The cold pipe into the valve is cold when the hot taps are running but turns warm after I've turned the hot tap off.

What do you think? Mixer valve or PHE sensor? Or other?

Thanks
Pete

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Post  mike Wed Jan 02, 2013 8:31 am

Bit confusing to say the least.
Mixer valve is a T
Lets say the left hand side is the water from the PHE ( plate heat exchanger) Is this side HOT ?
The vertical of the T is the cold (to mix the hot water)
And the right hand side is the mixed hot water out. Should be hot?

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Post  PeteMccarthy Wed Jan 02, 2013 8:53 am

Sorry if it was confusing.

When the hot tap is on:

The left hand side from the PHE is very hot.

The vertical is cold.

The right hand side mixed pipe is lukewarm.


Thanks
Pete


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Post  mike Wed Jan 02, 2013 9:27 am

Sounds like mixer valve.
But it is important that you are satisfied that the pump, PCB and sensors are delivering hot water to the mixer.
Mike

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Post  PeteMccarthy Wed Jan 02, 2013 2:00 pm

The pipe from the PHE to the valve is very hot and the mixed pipe (exiting the valve) is significantly cooler. So there must be too much cold water being allowed into the valve. Does that then sound like a faulty valve?

So I guess it's just a case of turning off the mains water supply, running the taps until they've drained and then swapping the old mixing valve for the new one?

Is there anything else I should know?

Thanks
Pete

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Post  mike Wed Jan 02, 2013 2:09 pm

You have answered your question.
And there will be nothing else as long as you checked ref my last post.
Order new valve
And EXTRA set of rubber washers as they can be tricky at times.
Perhaps a bit of silicone grease will help on the rubber washers to help stop them move / catching / braking / leaking.
Mike
MGC/H2O
Norfolk.
All advice given in good faith and more so with out being in front of the unit.
Nothing in this world beats experience.

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Post  PeteMccarthy Wed Jan 02, 2013 2:16 pm

Mike, thank you so much for all your advice. I'll give that a go...

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Post  PeteMccarthy Sat Jan 05, 2013 8:05 am

Hi Mike,

I think I've solved one problem and created another.

I've changed the mixer valve over and now the temp of the outgoing mixed pipe is the same as the PHE pipe going into the valve. So that's good.

But the temp of both although warmer than before, aren't very hot (just quite warm) and again doesn't last longer than 10 mins before it goes cool.

The D shaped pipe from the cylinder to the heat exchanger is very hot but again doesn't last that long before it cools.

The pump appears to be working, judging by the noise and voltage.

I did have trouble getting the old mixer valve off and knocked the pipes, sensor about a bit. I don't know if this made a difference?

Any suggestions would be appreciated.

Thanks
Pete

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Post  mike Sat Jan 05, 2013 8:26 am

Well if the pipe above the PHE is going cold.
Is the unit FULL?
And to check you must drain some water from the unit. And ENSURE that the water drops from the header tank.
If it does not, then the cold feed and or vent may be blocked.
What about the other side of the PHE ? What temperature is that? The same? Cold?
Have you adjusted the mixer valve?
Mike

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Post  PeteMccarthy Sat Jan 05, 2013 12:58 pm

Thanks Mike. I'll check and post my results...

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Post  PeteMccarthy Sun Jan 06, 2013 1:01 pm

Hi Mike,

I drained some of the unit off and indeed the water level of the F&E tank dropped too. So the unit is full.

I'm at a bit of a loss now??? I've attached a picture which describes the temperature of each pipe while the hot taps are on. I'm only getting hot water for 7/8 mins before it cools right off.

As a reminder the pump appears to be working, the mixer valve has been change as well as both immersion heaters. Both green lights are on.

You've been very helpful up to now and any further suggestions would be gratefully appreciated.

thanks
Pete

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Post  mike Sun Jan 06, 2013 2:36 pm

Good pictures, they help.
What settings are the stats on?
As I can see that you are not using Gledhill immersion heaters / rod stats.
It seems to run for some time 7 to 8 minutes. Is the unit still hot after that time?
You need to check the pump / voltage when this is all going on and the PCB too.
The pump may be failing after it has ran / got hot.
Mike

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Post  PeteMccarthy Sun Jan 06, 2013 3:05 pm

I've put the stats up to max on each rod. I put the boost on earlier and although it took over an hour the top of the unit did get very hot. You're right, they are not Gledhill parts, but I didn't think that made too much difference?

I don't believe the unit changes temp after the pipes cool off but I'll have to double check this.

I checked the voltage of the pump (on the pcb) before I changed the mixer valve (and got 220v) but only straight after I turned the hot taps on. I'll check the voltage again when the pipes cool and see if I get a different reading.

I do know that the noise of the pump didn't change when it was hot or cooling off.

Again, thank you for your help.




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Post  sunny.sahdev Mon Sep 02, 2013 9:59 am

This is a clear as it gets. If you do however need basic fault finding info through a self check guide this link maybe able to help. - Gledhill Pulsacoil 3 Repairs (Just request the guide on this site)

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