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Mad Chemist
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Joined: 22 Jan 2007
Posts: 56
Location: York
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 Posted: Tue Aug 21, 2007 11:35 am Post subject: Boiler trips in and out |
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Hi
I have a Worcester 28 cdi boiler, and i've noticed that when people are in the shower it is constantly cycling on and off, I have a mixer shower, is this normal, as I would assume it should fire constantly?
It also takes a couple of minutes for the shower to run hot when you turn it on.
When the hot tap in the kitchen is run the boiler fires continually with no cycling.
Hope someone can shed some light on this
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ultimatehandyman
Site Admin
Joined: 16 Jul 2005
Posts: 9740
Location: Darwen, Lancashire
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| Posted: Tue Aug 21, 2007 12:06 pm Post subject: |
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Our combi does this.
I think the boiler shuts down when the shower is not calling for much hot water, then when the shower calls for hot water it fires up again.
When using the hot tap this will not happen as it is not thermostatically controled like the shower is.
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Mad Chemist
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Joined: 22 Jan 2007
Posts: 56
Location: York
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| Posted: Tue Aug 21, 2007 12:21 pm Post subject: |
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That does make some sence, though there is one of these little clips on the mixer shower (to stop children scalding themselves) and I always have to take it past that to get a hot shower - don't know if this could be linked?
Also the pressure from the shower is pretty poor, much lower than my girlfriends electric shower, yet i've checked at the bath, and the hot is coming out of the tap at or around 10l / min, which i belive is the max for this boiler. Could the mixer be broken, or could it be that there isn't enough cold water to mix with the hot therefore the mixer is slowing the flow of hot?? (if that makes any sence at all)
MC |
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Jaeger_S2k
Senior Member
Joined: 19 Nov 2006
Posts: 2786
Location: North West, England, United Kingdom
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| Posted: Tue Aug 21, 2007 2:21 pm Post subject: |
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The boiler also cuts out when there isn't enough cold going through the heat exchanger to take away all the heat (making Hot Water) then because your calling for more hot water the boiler kicks off again.
The thermo valve in the shower will also be causing some of this as it operates the flow of hot independent of you.
Do you know if the shower valve is one for combi boilers?
Hinton Heating will be along soon and will answer better as he's the specialist (and will be unbearable to live with now I've said that!!!!!  )
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Mad Chemist
Member
Joined: 22 Jan 2007
Posts: 56
Location: York
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| Posted: Tue Aug 21, 2007 3:45 pm Post subject: |
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Ok, So it could be a lack of supply to the combi - have I got that right??
So to test this I can run the hot flat out in the kitchen, then turn the cold tap on, and see if this causes the boiler to fluctuate - would this work?
I just has a new bathroom fitted, and as the mixer shower seemed quite new i decided to re use it (the bathroom fitters said that would be fine), As i've not been in the house that long, i'm not sure if the boiler did it's cutting in / out before the bathroom was fitted.
The shower's a Mira mixer, the closest thing i can come up with on the net is this
http://www.mirashowers.com/onlinecatalog/big_image.jsp?image=dual_ev_ch_working_dial.jpg&icon=fino.gif&desc=Mira+Fino+E+Valve+Only+shown+in+Chrome
But this is more modern than mine, i'll look tonight and see if there is a model number on the shower. |
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Jaeger_S2k
Senior Member
Joined: 19 Nov 2006
Posts: 2786
Location: North West, England, United Kingdom
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| Posted: Tue Aug 21, 2007 3:58 pm Post subject: |
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The one you've posted is compatible.
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Plumbing system compatibility:
Fully modulating combi boilers and instantaneous gas water heaters
Gravity-fed hot and cold pumped water supply
Mains pressure hot and cold - unvented
Mains pressure thermal store |
Once you find the shower mixer model have a look here http://www.mirashowers.com/ and see if you can find it.
The problem with Combi Boilers is 2 fold, either you're not drawing enough hot water (So it's making more than you can take and shuts down) or you're not supplying enough cold (so you can't take as much as it's capable of making, gets too hot and shuts down).
There are also flow sensors that can feed the boiler the wrong info, might be one of them. Have you looked at the boiler instructions specs to see what it's capable of? Output Litres of hot at a sustained temp?
Doing what you're suggesting is working with valves that you control, the thermostatic valve in your shower works out with your control, it will balance the flow of Hot and Cold to give a safe temperature.
My experience of boilers is limited but Hinton Heating will be on soon he'll probably know off the top of his (now huge) head
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"Does my bum look BIG in this?" Wit's a Ba' Hair in Metric?
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Hinton Heating
Gas/Heating Expert
Joined: 16 Jan 2006
Posts: 4296
Location: Bournemouth
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| Posted: Tue Aug 21, 2007 11:51 pm Post subject: |
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ermmm..
Think J2SK has said it all really...
From the sounds of it, the boiler is doing its job... As previously said, you'll need to establish if shower mixer is suitable for combis.
I'm not really a shower expert.
If the shower is running at a fairly even temperture, then I'd say its alright.
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Inky Pete
Senior Member
Joined: 03 Feb 2006
Posts: 99
Location: Cheshire
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| Posted: Wed Aug 22, 2007 8:38 am Post subject: |
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I had a problem with my Baxi 105 combi-boiler when it first went in, couldn't get a decent flow rate at a stable temperature through the mixer shower. Problem was, the hot water was set too hot on the boiler. To get the shower temp I like, I was using loads of cold and just a trickle of hot, so the boiler kept cutting in and out.
I lowered the HW temp setting on the boiler, on the Baxi there's a knob on the control panel for this, so we're now using a greater proportion of hot to get the same temperature of shower. The boiler doesn't cut in and out, and both shower temp stability and pressure are much better. |
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ultimatehandyman
Site Admin
Joined: 16 Jul 2005
Posts: 9740
Location: Darwen, Lancashire
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| Posted: Wed Aug 22, 2007 8:56 am Post subject: |
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I have repaired a few Mira 415 showers as we have one and an house that I sold a while back had one in.
The parts are very expensive for them and if I remember rightly it is about £45 for a cartridge for the 415. I think ours is on it's way out again as it does not do a good job of regulating the water at all, one minute it is ok and the next minute it is either boiling or freezing.
I think next time I will get a different make!
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dewaltdisney
Senior Member
Joined: 20 Jan 2006
Posts: 576
Location: Essex
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| Posted: Wed Aug 22, 2007 8:57 am Post subject: |
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In the summer month the mains incoming cold water is much warmer. I have a combi and Mira shower valve an I notice that I have to turn it down into the blue zone to reduce the water temperature to an acceptable level. In winter the valve is up right at the top of the hot zone.
You can turn of the annoying preset red button stop by taking the knob off and moving the red locking ring around. The Mira instruction book download shows you how. The other thing is that a flow restrictor may have been left in the valve during assembly. Again the book explains this.
Hope this helps
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Mad Chemist
Member
Joined: 22 Jan 2007
Posts: 56
Location: York
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| Posted: Wed Aug 22, 2007 1:55 pm Post subject: |
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Hi,
It is a Mira 415, checked it last night.
Good info about removing the red safety switch, as it's annoying, and i'll look for a flow restrictor while i have it appart.
The shower runs at a constant temperature, but the volume of water is pretty poor.
I think i'm confusing myself though, because my initial issue was that the boiler was modulating on and off, and i was concerned that this was indicating a fault. I'm now fairly happy that the boiler is doing it's job.
In the process i've also realised how poor the flow of water from the shower is. I think i'll have a good look at the system, and take some measurements of flow at differant points then come back if i have any more questions.
Thank you all for your help.
MC |
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Hinton Heating
Gas/Heating Expert
Joined: 16 Jan 2006
Posts: 4296
Location: Bournemouth
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| Posted: Wed Aug 22, 2007 6:30 pm Post subject: |
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think a 28 kw will only give 9.5 lt/min at a temp rise of 35c
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