Not fully sure as it’s my mother in laws boiler but she thinks it started up with the new controller (installed only as old one was outside in a garage with boiler). I don’t think there’s a manual valve, she’s never had to adjust any valve to switch btw HW / CH ..
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CH on heats HW, and HW on heats CH (Ed.)
- Thread starter Shimlasun
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There is no cylinder stat visible
And OP can't see a motorised valve
So perhaps it was built with gravity HW
There might be a cyltrol or similar on the cylinder return.
They are still available but very expensive.
I used to have one but converted to fully pumped which was better.
And OP can't see a motorised valve
So perhaps it was built with gravity HW
There might be a cyltrol or similar on the cylinder return.
They are still available but very expensive.
I used to have one but converted to fully pumped which was better.
Thank you. Is the cyltrol another way of switching btw supplying CH and HW… if we don’t have a motorised or manual valve? Just trying to understand as much as I’m able to!
Is there any chance this is the controller being installed incorrectly (wired badly) if it’s been an issue since then? My mother in law hasn’t been able to get the chap who installed it to take a look (not answering messages) and we’re just not sure whether to now get an electrician to look at the wiring of the controller, or a heat engineer to look at all the valves/system.
Is there any chance this is the controller being installed incorrectly (wired badly) if it’s been an issue since then? My mother in law hasn’t been able to get the chap who installed it to take a look (not answering messages) and we’re just not sure whether to now get an electrician to look at the wiring of the controller, or a heat engineer to look at all the valves/system.
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Engage a heating engineer.
If (and this is the big question) you do have a gravity system, the HW should be independently controlled.
However, if central heating is called for, the heating and hot water will come on together. This is normal behaviour.
What's interesting, is the A27-HW doesn't have an option for allowing this behaviour - it doesn't have a 'Gravity' mode.
If you are comfortable, with the power to the controller safely isolated, could we have a photo of the wiring behind the A27-HW?
Ok thanks. Just to add, thanks for changing my post title, but when the HW is heating, the CH doesn’t come on a littke bit, it comes on full blast and doesn’t switch off when the thermostat reaches target temp, because of course the HW wouldn’t be linked to the thermostat. So it overshoots and gets the house very warm. It’s very odd!
A cyltrol is a thermostatic valve that stops the boiler heating the cylinder once the cylinder is fully heated. There is also Drayton equivalent. I had one in a very old installation. If you photograph the pipe near the bottom of the cylinder, that goes to the boiler, we might see it.
Mine was 30 years old and jammed. I bought a replacement but didn't use it as there is a better way. I think I eventually sold it on ebay for about £130.
I found an even older brass valve under the floor, winter/summer, to manually control the radiators or cylinder.
Mine was 30 years old and jammed. I bought a replacement but didn't use it as there is a better way. I think I eventually sold it on ebay for about £130.
I found an even older brass valve under the floor, winter/summer, to manually control the radiators or cylinder.
Thank you, that’s interesting, I wonder how we can figure out if it’s a gravity boiler… yes we’ll have a go at taking the photo, would you mind taking a look if we send in the morning … I don’t think I can manage that one myself
Thanks for explaining
had a look around can’t see anything like that… here’s a picture of the pipes at the bottom of the cylinder. Wow £130 eeek! Hope it’s not one of those! Hello all, I think we now know it is a gravity system as suspected from earlier posts. We weren't able to get the front off the controller unfortunately (mother in law too worried it was dangerous!). But please could someone tell me whether it's possible for the EPH A27-HW to work with a gravity system, or whether we might in fact have the wrong type of controller?
From the manual, undo the couple of screws at the bottom and flip the controller upwards...
As earlier, the A27-HW doesn't have a "Gravity mode". It isn't the correct controller for a gravity system.
It seems that the installer has cobbled the HW and CH to come on together. This will only be seen by looking at the wiring behind the A27-HW (or in the separate wiring centre, if you have one).
Safely isolate the power to the boiler and controls first, there should be little risk to simply remove the cover. Just don't go poking around yet!
Thank you very much for this RandomGrinch. Unfortunately we're not with my mother in law anymore, she lives 5 hours away!.. we were visiting her last weekend, so now trying to help remotely. She got into this fix as the original electrician that fitted the A27-HW as not been helpful in coming back to sort the problem out, took away her manual on her boiler (where it presumably says its a gravity system) saying he wasnt sure what to do but would look into it, subsequently cancelled an appointment and hasnt offered another one ... he's giving her the run around so we're not going to continue chasing him, he either doesnt know what to do or doesnt want to sort out his own mistake. She had a heating engineer out yesterday, who seemed to say like you that it was the wrong controller, but wanted her to go back to the original electrician first. We're going to get back him on Monday to explain more fully that we've lost confidence and don't want to deal with him any more. He's (the guy that visited yesterday) advised a Honeywell Home 2 Channel programmer (ST9400C) instead. Would you say this is a good option? He didn't seem to think the current controller could be rewired to make it work so I think we're going to draw a line under that despite the extra expense of getting a new controller. Unfortunately he said he would need to get his electrician colleague to fit this controller for us if we did go ahead, rather than fit it himself ... so we're getting sent around the houses quite a lot!!
The only way the EPH can be made to work with a gravity system, is to ensure the CH is only programmed to come on when the HW is also on; that would be a big faff.
A new controller with a Gravity mode would be far more convenient.
The ST9400C has to be configured as a 'mini programmer' to control a Gravity system - this mode disallows some functions and could be a little confusing.
Something like a Drayton LP822 may be a more straightforward controller - it has a specific Gravity mode switch on the back.
Alternatively, even a Hive smart stat has a gravity mode.
This may be a good idea, because as you said earlier...
Even if the EPH was wired for both CH and HW to always come on together, the thermostat should still be able to open the pump circuit; stopping the CH.
This was one of the reasons I wanted to see behind the EPH - the previous electrician seems to have left a right bodge, that needs to be sorted out.
Yes we're not at all pleased with him, everyone makes mistakes but he should have helped to sort it out and not left her with a system that doesn't work properly. It's a shame we didn't get a picture of the wiring whilst there to share with you...
Thanks very much for the advice re Drayton, we definitely need something straightforward.
What functions would be disallowed on the Honeywell if that was used?
She has a EPH Digital RF room thermostat and receiver - can these be kept when changing to the Drayton or Honeywell controller?
Thanks very much for the advice re Drayton, we definitely need something straightforward.
What functions would be disallowed on the Honeywell if that was used?
She has a EPH Digital RF room thermostat and receiver - can these be kept when changing to the Drayton or Honeywell controller?
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I am an electrician not a heating engineer, but I think the back plate on that controller is common to a number of makes, it looks the same as the one on my Drayton Wiser, and also Hive. I looked at the Wiser instructions and like EPH it does not seem to have an option to work with gravity DHW systems, however the Hive does, it has a software option so the two relays can be arranged one to run pump, and one to run boiler, which in theroy will allow DHW without the central heating running, although not the other way around, there is no way to turn off DHW when central heating is running.
I used Nest Gen 3
because one has access to the com terminal it can be wired to only run the pump when CH is required, and the option of a ½ hour slot in the summer, allowed me to run the central heating boiler without pump 4 times a week, it would run for around 20 minutes each time, however when I had solar panels fitted, I also had an iboost+ fitted, to heat DHW with the solar power, and it tells me how much saved, which is basic how much energy is being used to heat the DHW.
This was a lot lower than expected, around 2.5 kWh per week, OK only heats top of cylinder, so no good for a bath, but oil was using around 25 kWh per week, as it has to also heat the boiler and all the pipe work, so in summer it would have been cheaper to use the immersion heater to using oil.
Also I found even with the pump not running, the radiators did get slightly warm, so I fitted motorised valves to stop the water going through the CH, but was advised not to fit them to the DHW as the boiler uses the DHW to cool down, how true that is I don't know, but that's what my oil guy told me, so I did as he said. I have no way to turn off DHW heating from the boiler, so today I never run the boiler for DHW only, but it does heat DHW when central heating is running.
So if I was starting today with the knowledge I now have, I would not even try to get boiler to heat DHW on its own, if I wanted DHW only I would use an immersion heater, it is cheaper that way, I still have Nest Gen 3 so can set it to just heat DHW, but I don't, I now use a single channel Wiser thermostat to run the central heating, in parallel with the Nest as Nest is in the hall, and the hall cools slower than the living room, and Nest will not connect to TRV heads, Wiser however will, so idea is to slowly replace the stand alone programmable TRV heads of linked programmable TRV heads at least in key rooms.
So with what I know now, I would say simply use an immersion heater in summer, and leave CH as it is.
I used Nest Gen 3
because one has access to the com terminal it can be wired to only run the pump when CH is required, and the option of a ½ hour slot in the summer, allowed me to run the central heating boiler without pump 4 times a week, it would run for around 20 minutes each time, however when I had solar panels fitted, I also had an iboost+ fitted, to heat DHW with the solar power, and it tells me how much saved, which is basic how much energy is being used to heat the DHW.This was a lot lower than expected, around 2.5 kWh per week, OK only heats top of cylinder, so no good for a bath, but oil was using around 25 kWh per week, as it has to also heat the boiler and all the pipe work, so in summer it would have been cheaper to use the immersion heater to using oil.
Also I found even with the pump not running, the radiators did get slightly warm, so I fitted motorised valves to stop the water going through the CH, but was advised not to fit them to the DHW as the boiler uses the DHW to cool down, how true that is I don't know, but that's what my oil guy told me, so I did as he said. I have no way to turn off DHW heating from the boiler, so today I never run the boiler for DHW only, but it does heat DHW when central heating is running.
So if I was starting today with the knowledge I now have, I would not even try to get boiler to heat DHW on its own, if I wanted DHW only I would use an immersion heater, it is cheaper that way, I still have Nest Gen 3 so can set it to just heat DHW, but I don't, I now use a single channel Wiser thermostat to run the central heating, in parallel with the Nest as Nest is in the hall, and the hall cools slower than the living room, and Nest will not connect to TRV heads, Wiser however will, so idea is to slowly replace the stand alone programmable TRV heads of linked programmable TRV heads at least in key rooms.
So with what I know now, I would say simply use an immersion heater in summer, and leave CH as it is.
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