Barryscotland Posted July 22, 2022 Share Posted July 22, 2022 Hot water is controlled via our wunda smart hub and as far as I can tell the only option is to have it on a timer, there is no way to monitor or control the actual hot water temperature other than the boiler is set to 70 degrees so if the return side of the boiler is at 70degrees it cuts out so in theory if its left on it should keep the water at 70degree but when ive tried this it never cuts out even after a few hours which may be because the tank is 20m worth of pipe away so its cooled enough by the time it gets from tank back to boiler to be below 70 degress even though hot water is now above 70? Im wanting to put a solar diverter onto my solar pv for any unused electric to heat the hot water but don't see how I can stop the boiler firing up on its usual timer settings when the water has already been heated by solar power. Its a gas system boiler and a pressurised 260l cylinder, 4 in the household and currently boiler is on for half hour in the morning and half hour at night which provides enough hot water for 4 showers and normal day to day needs. Also is it possible to have the towel rails which are on a seperate chanel kick in with the hot water? Link to comment Share on other sites More sharing options...
ProDave Posted July 22, 2022 Share Posted July 22, 2022 More details, photos of valves, and other controls on or around the cylinder etc? Why not just turn the HW boiler heating off, and only turn it on manually if there is not enough sun? Link to comment Share on other sites More sharing options...
kommando Posted July 22, 2022 Share Posted July 22, 2022 I have a thermostat on the hot water tank at 2/3 up, this overrides the boiler and turns it off once the hot water tank reaches 65C regardless of the boilers own temperature setting unless hot water is also needed for the radiator circuit. You would need to check the boiler and heating wiring plus valve controls and see if there is the option to add a thermostat. Even with the thermostat the boiler is turned off in summer and only turned on if the PV diversion has not heated the water enough, well depends on the temp of the water, for 5 or 10C the immersion is used for 15 mins rather than use the boiler as that needs to heat itself and all the water in it before it can heat the tank which is inefficient. Link to comment Share on other sites More sharing options...
JohnMo Posted July 22, 2022 Share Posted July 22, 2022 Does your cylinder have a thermostat? You need the thermostat to call for heat and shut off heat based on your time schedule. So the wiring goes from the thermostat via the time switch or your smart hub to the boiler. So your smart hub isn't really that smart! Link to comment Share on other sites More sharing options...
JohnMo Posted July 22, 2022 Share Posted July 22, 2022 If you just want to heat the towel rails from you central heating, you will end up with the boiler short cycling if they are the only thing asking for heat. Have you thought about making them dual fuel, by adding electric elements? Then you can add a simple time switch to heat the rail when you out wet towels on it. Link to comment Share on other sites More sharing options...
saveasteading Posted July 22, 2022 Share Posted July 22, 2022 Just now, JohnMo said: adding electric elements? Then you can add a simple time switch to heat the rail when you out wet towels on it. I have one of those. It works really well, especially with a simple control (toolstation I think) where one push switches it on for an hour. Retrofit was complex with wires to the bathroom from an adjacent dry room. recommended though. Link to comment Share on other sites More sharing options...
Barryscotland Posted July 22, 2022 Author Share Posted July 22, 2022 1 hour ago, ProDave said: 1 hour ago, ProDave said: Why not just turn the HW boiler heating off, and only turn it on manually if there is not enough sun? I could do if I knew how hot the water was but no way of checking other than running a tap. Will add photos of the set up see if theres anything that can be done but without changing away from the Wunda set up I dont think there is. Link to comment Share on other sites More sharing options...
Barryscotland Posted July 22, 2022 Author Share Posted July 22, 2022 Wunda hub has three channels an each operates one of the valves. Hot water, towel rails, ufh manifold Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2022 Share Posted July 22, 2022 The grey boxes on the cylinder…..are they not immersion and cylinder stat? I’m pretty sure without that stat and a zone valve in play, you won’t get a G3 sign off for that system. Link to comment Share on other sites More sharing options...
ProDave Posted July 22, 2022 Share Posted July 22, 2022 10 minutes ago, Nickfromwales said: The grey boxes on the cylinder…..are they not immersion and cylinder stat? I’m pretty sure without that stat and a zone valve in play, you won’t get a G3 sign off for that system. +1 to that. Unscrew the covers and I bet you will find a thermostat dial under there. Set it to 50 degrees, plenty hot enough for hot water and that leaves room for solar PV to heat it further. There will be 2 or more dials, work out which one is the cylinder thermostat dial, that is the one that needs to be turned down. The immersion thermostat needs to remain higher. Post a close up picture of what is under the two grey covers. Link to comment Share on other sites More sharing options...
JohnMo Posted July 22, 2022 Share Posted July 22, 2022 But doesn't the thermostat need connecting in to the boiler control circuit, to do anything. The middle grey box, which I assume is the thermostat for the cylinder is not connected to anything as there are no wires coming out of it. Link to comment Share on other sites More sharing options...
PeterW Posted July 22, 2022 Share Posted July 22, 2022 Who’s done the install as there has to be an interlock between heat source and the unvented cylinder as a couple of people have said to meet MIs and Building regs / warrants. Link to comment Share on other sites More sharing options...
Barryscotland Posted July 22, 2022 Author Share Posted July 22, 2022 (edited) 33 minutes ago, PeterW said: Who’s done the install as there has to be an interlock between heat source and the unvented cylinder as a couple of people have said to meet MIs and Building regs / warrants. I asked the plumber what causes it to cut out when temp reached, his reply was the boiler cuts out when it sees the return temp at 70 which is what water should be to kill germs, in practice it’s never cut out unless turned off by the timer Edited July 22, 2022 by Barryscotland Link to comment Share on other sites More sharing options...
ProDave Posted July 22, 2022 Share Posted July 22, 2022 The thermostat probably is connected. The bottom grey box appears to have 2 wires coming from it. One goes to the switch, that is the immersion heater feed. the other wire goes into the wiring centre, so that is almost certainly the cylinder thermostat. Take that bottom grey cover off and take a close up photo of what is inside. 21 minutes ago, Barryscotland said: his reply was the boiler cuts out when it sees the return temp at 70 Plumber is as thick as mince. It should cut out when the cylinder thermostat reaches it's set temperature which will cause the motorised valve to close and the "call for heat" to the boiler to stop. Your "smart" controller is just doing the job of a central heating time programmer. The top grey box is probably a second immersion heater, not in use. Link to comment Share on other sites More sharing options...
JohnMo Posted July 22, 2022 Share Posted July 22, 2022 If you really want to kill everything that may be in chlorinated water, then 60 degC is enough, you don't need it at 70 degC. Bet the thermostat is set at 70 degC or very close to it. That is why the boiler is never switching off Link to comment Share on other sites More sharing options...
ProDave Posted July 22, 2022 Share Posted July 22, 2022 2 hours ago, Barryscotland said: Have you got a leak? third pipe from left front row. Link to comment Share on other sites More sharing options...
PeterW Posted July 22, 2022 Share Posted July 22, 2022 1 hour ago, Barryscotland said: I asked the plumber what causes it to cut out when temp reached, his reply was the boiler cuts out when it sees the return temp at 70 which is what water should be to kill germs, in practice it’s never cut out unless turned off by the timer Does your plumber have a G3 or equivalent ticket to install unvented cylinders ..? As that is very wrong advice ..!!! It is a mandatory requirement to interlock the control of the heat source to the thermostat on the tank. And the germs/legionella stuff is rubbish … Link to comment Share on other sites More sharing options...
Barryscotland Posted July 22, 2022 Author Share Posted July 22, 2022 5 hours ago, ProDave said: Have you got a leak? third pipe from left front row. Just checked and not on that one but one is a bit damp at top with a rusty line, should I be worried that it looks rusty?? Link to comment Share on other sites More sharing options...
Barryscotland Posted July 22, 2022 Author Share Posted July 22, 2022 4 hours ago, PeterW said: Does your plumber have a G3 or equivalent ticket to install unvented cylinders ..? As that is very wrong advice ..!!! It is a mandatory requirement to interlock the control of the heat source to the thermostat on the tank. And the germs/legionella stuff is rubbish … No idea about q3 but would presume so, we never got any certificates for the water or gas side of things, hopefully nothings needed when we finally go to get house signed off. It was the sparky that wired everything up and he did seem to be the most competent out of all the tradesmen we’ve had in so I’d think it was done correctly. Link to comment Share on other sites More sharing options...
ProDave Posted July 22, 2022 Share Posted July 22, 2022 5 minutes ago, Barryscotland said: No idea about q3 but would presume so, we never got any certificates for the water or gas side of things, hopefully nothings needed when we finally go to get house signed off. It was the sparky that wired everything up and he did seem to be the most competent out of all the tradesmen we’ve had in so I’d think it was done correctly. I would chase the plumber before it's too late. you need him to fill in and sign the comissioning sheet, either the one supplied with the cylinder or the generic version. Certainly in our case building control wanted to see that along with the gas safe certificate and electrical installation certificate. Hopefully it is all wired properly and you just need to adjust the cylinder thermostat. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2022 Share Posted July 22, 2022 13 minutes ago, Barryscotland said: No idea about q3 but would presume so, we never got any certificates for the water or gas side of things, hopefully nothings needed when we finally go to get house signed off. No certs for water or gas!?!?! You won't get signed off until your gas install is registered online with the GSR ( Gas Safe Register ). Have you finished paying the plumber? 6 hours ago, ProDave said: Plumber is as thick as mince. But of less use, it appears.... Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2022 Share Posted July 22, 2022 6 hours ago, Barryscotland said: I asked the plumber what causes it to cut out when temp reached, his reply was the boiler cuts out when it sees the return temp at 70 which is what water should be to kill germs, in practice it’s never cut out unless turned off by the timer Complete and total bollocks. 1 Link to comment Share on other sites More sharing options...
Marvin Posted July 22, 2022 Share Posted July 22, 2022 37 minutes ago, Nickfromwales said: Complete and total bollocks. You feel this is not quite the right reason then? Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 22, 2022 Share Posted July 22, 2022 1 hour ago, Marvin said: You feel this is not quite the right reason then? Most plumbers can’t wire up an S plan, so they come up with all sorts of incentive ways to dodge those mystical 5 wires of the zone valve….. For G3 you need fail safe on the controls. That is via the cylinder stat. An UVC is a potentially explosive device, and relying on just the boiler stat is a defo no-go. He’s not only careless, but he’s dangerous, and clearly doesn’t know the requirements of G3. Get him gone and get the system made safe plz!! 1 Link to comment Share on other sites More sharing options...
PeterW Posted July 23, 2022 Share Posted July 23, 2022 20 hours ago, Barryscotland said: Wunda hub has three channels an each operates one of the valves. Hot water, towel rails, ufh manifold Right so looking at this pic he has a pair of wires heading into the Megaflo control panel (the lower one) and that should be wired as per page 19 of the installation manual. But from there, the wires marked 1-2-3 should go to the wiring centre and the zone valve controller for the cylinder as per wiring on page 19/20 of the manual If he has followed this correctly then the supplied zone valve (that has a micro switch in it) will trigger the boiler to fire when it’s needed using the live switched terminal 16. If the boiler needs a NV connection then it’s a bit more complicated but it’s all done with the valves. Tank temp / cutout is then driven by the correct thermostats on the tank ..! All of this is in the installation manual if he read it …. 1 Link to comment Share on other sites More sharing options...
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