Shower providing only intermittent hot water

keefzip · 25 Jun 2008

Hi

I'm having a bit of a problem with my newly installed thermostaic shower (Triton Tyne). I the morning, it starts to get hot, but then after a few minutes goes cold. If left alone, it sometimes gets warm again, but will then go cold. I can, however, get a constant supply of hot water from all taps in the house.

1) Boiler make / model (gas or oil)

Worcester CD24i Combi boiler

2) What is / is not happening.

As mentioned above

3) Has ANYTHING else been done or changed recently.

Only the shower has been installed. The previous shower was an electric one, so this is the first time that the boiler has had to provide hot water to the shower.

4) When did the problem start?

as above

5) When does it happen? eg, heating coming on or going off.

In the morning, mainly.

6) Anything else you feel may be of relevance.

Flow rates (litres per minute)
for morning are:
5 hot, 8 cold

For the evening are:
8 hot, 11 cold

I think the pressure is fine, but not had it checked. The water temp on the comi boiler is set on about halfway. I've changed this from minimum to max, but it doesn't seem to make any difference.

Thanks in advance for your help - I need it, as not having a hot shower after spending so much money decorating the bathroom is a nightmare!

Thanks

Tim[/u]

plummerman · 25 Jun 2008

did it work ok after it was fitted and how long did it last before it failed. from wot you've said it's doesn't sound like a problem with boiler. first thing id check would be the filters on in the inlet connections! secondly if it's never really work right i'd check to see if the pipe work is not crossed. I.E hot going to cold inlet and visa versa. Failing that if all seems fine it could just be a faulty thermostat cartridge. if in guarantee triton will usually come out and replace

keefzip · 26 Jun 2008

Thanks for that advice. I'll look into those possibilities.

If there was a problem with the shower itself, would it not work all the time, rather than work in the evening, but not in the morning?

As for the filters - do you mean I should check to make sure that they are not blocked?

If the thermostat cartridge was broken would if still work intermittently, in the evening, and not in the morning?

beardosh · 26 Jun 2008

I also experience the same issue after recently going from an electric shower to a Triton Mimosa Mixer. Have an Ideal Response 120 (unfortunately, from the look of the posts on this site). Again, all the taps give continuous hot water but the shower fluctuates every 30 seconds or so. How can checks be made as you cant get to the shower as all the 'bits' are behind the tiled wall?

plummerman · 26 Jun 2008

Sorry i've just re- read your orginally post long day yesterday. you say you've hot different pressures on your hot and cold systems. Mixer shower work on a differential pressure of 0.1 between the two supply's. So without actually looking at it id say the valve is working fine and is shutting down due to the fluctations. A balancing valve should sort this problem

keefzip · 26 Jun 2008

but my system is a combi, so wouldn't the pressures of hot and cold be the same - the flow rate is what is different, but isn't that always the case as the combi slows down the flow rate so it can heat the water?

MJN · 26 Jun 2008

It sounds to me like a classic case of a split diaphragm in the diverter valve - extremely common on your boiler.

The diaphragm moves in response to the differential pressure gradient of you drawing hot water... If the diaphragm is split is requires a greater flow in order to trigger the firing of the boiler (and divert water through the secondary heat exchanger).

The situation can often occur that the high flow through taps is sufficient to keep the boiler fired, however a shower by virtue of it mixing water with the cold draws a reduced amount of hot water and hence can cause the diaphragm to fail to remain open.

It's easy to check whether this is what's happening or not - turn the shower on and confirm it is 'misbehaving' then look into the boiler from the underside and you will see the plunger on the diverter valve activating a microswitch. If this plunger periodically retracts then that's (probably) your problem.

It's worth noting that if the diaphragm has perished then you should check the HW inlet filter on the shower as this could well have caught the bits that inevitably come astray.

Mathew

beardosh · 27 Jun 2008

This makes sense because watching my boiler when the shower is on and it continually turns itself off and on as the shower changes temperature. as pointed out in another thread, I will soon be saying goodbye to the current boiler so hopefully this problem should clear when the new one is in place.

Volks2u · 6 Jul 2014

I realise that this is an old thread, but I have a similar issue:
We have an early Glowworm Swiftflow combi (mid 90's) boiler. The shower was fitted by me by just extending hot/cold pipework from the bath. No pressure equalizing balancing valves are fitted. It worked perfectly for the first few months (can't remember the season), but during summer when the heating is OFF the shower displays these symptoms.
We've had the shower serviced by British Gas and an independent gas engineer over the last couple of years and both say there is an issue with the shower ! However the shower works perfectly during winter when the heating is ON.
I've checked/rinsed the filters and rinsed the thermostatic valve, no change.
If I feel the hot feed pipe to the shower when the symptoms are displayed it's cold when the shower runs cold.
I note the post above which indicates a split diaphragm in the diverter valve. Could this be my problem ?
When its working properly its great, but now its summer....
I'm quite handy, but leave the gas servicing to the experts ! I'd be grateful if anyone who responds could be quite specific about the part/s that need to be checked/replaced since I'm not confident the previous checks have been thorough enough !!

Many thanks in advance.

MJN · 6 Jul 2014

In the winter the temperature of the incoming mains water is obviously a lot lower and, as a result, the shower control will require is proportional lower amount of cold feed to maintain the required output. Given the constant flow rate this will mean a higher amount of water coming through the boiler.

I'm not familiar with your boiler but if it's flow detection and/or diversion is performed by a diaphragm then a failing can cause symptoms like you've described. In the summer months, where less heated water is required by the shower, the flow can be insufficient to keep the diaphragm adequately displaced.

When the problem occurs try opening a hot tap to see if this 'cures' it. You might need to experiment a bit with flow rates - you need enough to tip push the diaphragm over its activation threshold but not too much that insufficient hot water reaches the shower. Even with the latter you should hopefully see the boiler firing continuously (which presumably it isn't during your problem periods).

Volks2u · 18 Jul 2014

Thanks, I'll have a play and note what happens.

Volks2u · 29 Oct 2014

Its been a while but had the boiler serviced again and the plumber checked the shower. He thought it was cold water bypassing the mixer seals and fitted a one-way valve to ensure that the cold water wasn't going down the hot pipe. Unfortunately I was distracted with work so didn't get the flow control adjusted. True to form the shower worked perfectly whilst he was testing it, but has gone back to its old ways. What it does confirm is that the boiler is intermittently kicking-out cold water. If I feel the pipe between the boiler and the one-way valve it does run cold, so although there could be cold water bypassing the seals. there is very definitely cold water coming from the boiler so this must be the issue. On the basis the shower doesn't use much water it takes a full minute to clear the clear water through when the boiler kicks in. I'll have to speak to the plumber, but it would appear the shower isn't the problem !

Tipper · 30 Oct 2014

If you take off the shower head does it do it then? Or when you run a bathroom hot tap at the same time?

I ask because it could be that the shower head flow is just too low for the boiler and therefore it is cycling on and off, hence the changeable water temperature. If it has a flow restrictor/economiser gadget, try removing it.

Volks2u · 30 Oct 2014

Like MJN I think you are correct, what I didn't mention above was the fact that when I run the hot tap the shower is consistently hot.
This AM I also watched the boiler cycling on/off as I had my shower, obviously the cold water came through circa 30secs later, not immediately.

So can anyone tell me how we can adjust the diverter valve on our Glowworm Swiftflow combi (mid 90's) boiler?
The instruction manual isn't too helpful.

Volks2u · 28 Oct 2015

Update... Tipper was correct. I managed to get hold of the plumber who originally fitted the shower and his suggestion was to remove the shower head. With the head removed the shower remained consistently hot.
Solution: bought a shower head with "bigger holes" !! I got it off ebay for £11 delivered. It doesn't have the rub-clean head, but importantly the shower is working fine now...result!

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Shower providing only intermittent hot water

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