Nightmare boiler setup, please help.

[Squuiid]

Likely there is no way of having central heating without domestic hot water, if the boiler is running you have domestic hot water, however it is likely wired so you can have domestic hot water (DHW) without central heating (CH) the idea is if pump does not run, then no CH, however this is a bit hit and miss, once the CH is warm thermo syphon will likely keep it running at least upstairs, the plumber and oil heating engineer I got in scratched their heads and hadn't a clue, I did not care, I designed the wiring from scratch.

Firstly, thank you everyone for the responses. They've been extremely helpful and I really appreciate you taking the time to post.

The above quote is exactly what we have I think. We can have Hot Water (HW) without Central Heating by hitting the "Summer switch" as this turns off the Wilo 2 pump, preventing water from circulating to the downstairs Central Heating (CH1). Upstairs Central Heating (CH2) can only come on when the Hot Water is on as the programmer is just controlling the Wilo 1 pump on and off on terminal 4. Is that right?

My plan is to try and make this somewhat smart, using the existing 2 channel programmer for now (money is tight), and maybe even a Tado 2-channel smart thermostat and extension in future.

My question then is what would happen if I wired the Warmflow boiler Thermostat to terminal 3 (HW ON) to turn on the boiler, and then both Wilos to terminal 4 (CH ON) and ensure that the central heating schedule always matches the hot water schedule? I'd replace the old, rusty radiator TRVs with new units to control room temperatures and just have the heating on a timer matching the hot water.

In the summer, both Wilos are disabled when no central heating is required, using the programmer. Hot water schedule can then be scaled back to twice a day.

In the winter, both hot water and central heating schedules would have to match, and if I wanted extra central heating on demand I would override both at the same time.
New radiator TRVs would, to a degree, help with efficiency.

Does this make sense? Or is there a much better way of doing this?
Would any harm come if the Wilo pumps were to inadvertently run without the hot water actually being on, or would it simply just push cold water around the system without issue?

 

[ericmark]

OK to start with in the winter you can turn DHW off, it heats up anyway, DHW schedule is only required in the summer.

Second is I found two pumps are a real pain, not a clue why two pumps, but I still need to add another relay to mine due to having two pumps. This is my plan and after all that I have made a mistake and need to add a second relay.

You talk about smart, and mine has some smart components, but they don't integrate in the way I would like, so I will admit my error in the hope you don't make the same error. Likely I would have been better with Sonoff or EvoHome, but to be frank although it does not integrate fully, it works well enough. But to improve I would need to replace all TRV heads and the wall thermostat, so that is not going to happen.

So you have to work out the final goal, and ensure all you do is progressing to that goal, and I hope others on this forum will help, as I will admit I am an electrical engineer not a heating and ventilating engineer so I don't know what is available on the market place. Some things I do know, Drayton and EPH both do three zone stuff, this thread page one @hard-work has posted a Utube link on three zones with opentherm, OK you have not got opentherm and I am assuming your using oil so not likely to ever get a boiler with opentherm, but the units shown will also work on/off (technical word for on/off is mark/space).

But I am getting ahead of myself, as said you have to set the goal, so I will talk about C Plan which I think you are running, there are actually three versions of C Plan.
Version one has no thermostat on the DHW so in winter DHW is as hot as CH water, and in summer you have to use simple time, this is what I have, and I would guess you have.
Version two adds a tank thermostat, this does nothing in winter, but in summer means boiler only runs when required, you don't need to guess how long.
Version three has a motorised valve on the DHW so summer or winter you can select DHW temperature. However version three has a problem, with no motorised valve the boiler cools by heating the DHW, but with a motorised valve the boiler has no where to cool to, and I am told causes extra strain on the boiler, modern boilers have it built in and have a warm up and cool down time where the flame goes out before the pump stops, this does not happen with older boilers.

I want to modify mine to version two, however either I need cables from the cistern to boiler area or use a wireless tank thermostat which is very expensive, I have looked at @hard-work link to EPH and I like the prices, but as yet done nothing due to lock down.

But again the goal, if you want a really smart system then Drayton Wiser seems the way to go, with integrated TRV which also have smart features and can remember how much heat is required to bring a room to the new temperature, but looking at around £1000 for complete system which you will never get back.

So I have used eQ-3 electronic heads on the TRV which is about the cheapest you can get, but to improve I need to renew all my TRV heads so in real terms not worth me starting again and moving to Drayton, Evohome or Tado. So back to the goal, what are your prepared to pay, and what do you want?

 

[Squuiid]

OK to start with in the winter you can turn DHW off, it heats up anyway, DHW schedule is only required in the summer.

Second is I found two pumps are a real pain, not a clue why two pumps, but I still need to add another relay to mine due to having two pumps. This is my plan View attachment 189125 and after all that I have made a mistake and need to add a second relay.

You talk about smart, and mine has some smart components, but they don't integrate in the way I would like, so I will admit my error in the hope you don't make the same error. Likely I would have been better with Sonoff or EvoHome, but to be frank although it does not integrate fully, it works well enough. But to improve I would need to replace all TRV heads and the wall thermostat, so that is not going to happen.

So you have to work out the final goal, and ensure all you do is progressing to that goal, and I hope others on this forum will help, as I will admit I am an electrical engineer not a heating and ventilating engineer so I don't know what is available on the market place. Some things I do know, Drayton and EPH both do three zone stuff, this thread page one @hard-work has posted a Utube link on three zones with opentherm, OK you have not got opentherm and I am assuming your using oil so not likely to ever get a boiler with opentherm, but the units shown will also work on/off (technical word for on/off is mark/space).

But I am getting ahead of myself, as said you have to set the goal, so I will talk about C Plan which I think you are running, there are actually three versions of C Plan.
Version one has no thermostat on the DHW so in winter DHW is as hot as CH water, and in summer you have to use simple time, this is what I have, and I would guess you have.
Version two adds a tank thermostat, this does nothing in winter, but in summer means boiler only runs when required, you don't need to guess how long.
Version three has a motorised valve on the DHW so summer or winter you can select DHW temperature. However version three has a problem, with no motorised valve the boiler cools by heating the DHW, but with a motorised valve the boiler has no where to cool to, and I am told causes extra strain on the boiler, modern boilers have it built in and have a warm up and cool down time where the flame goes out before the pump stops, this does not happen with older boilers.

I want to modify mine to version two, however either I need cables from the cistern to boiler area or use a wireless tank thermostat which is very expensive, I have looked at @hard-work link to EPH and I like the prices, but as yet done nothing due to lock down.

But again the goal, if you want a really smart system then Drayton Wiser seems the way to go, with integrated TRV which also have smart features and can remember how much heat is required to bring a room to the new temperature, but looking at around £1000 for complete system which you will never get back.

So I have used eQ-3 electronic heads on the TRV which is about the cheapest you can get, but to improve I need to renew all my TRV heads so in real terms not worth me starting again and moving to Drayton, Evohome or Tado. So back to the goal, what are your prepared to pay, and what do you want?

Thanks again for the detailed reply.
There are 13 radiators with TRVs in the house and 2 without (which will run constantly whenever the CH is on as there is a damp problem in that room). Our first month's oil bill was £300, hence the urgent need to look at this.

All radiator TRVs are old and rusty and need replacing. A Tado system, using the method I described in the post above, while not perfect, would offer far greater control and set me back £850.
Sure, I would need to have the same timers for HW and CH, but that is minor compared to spending so much on oil.

I didn't quite understand what you said here, "OK to start with in the winter you can turn DHW off, it heats up anyway, DHW schedule is only required in the summer."
Would you mind clarifying that bit? Sorry, I'm learning all of this now for the first time and this boiler type is definitely new to me.

 

[ericmark]

I have 15 radiators, and filled up with oil start of winter, and some time in Feb so not cost me that much, I have swapped all main house TRV's one radiator does not have one in bathroom, I have 4 Energenie TRV heads which are wifi and 5 eQ-3 heads which are bluetooth, so every room except shower room and bathroom have their own schedule set so rooms only heated when required, the non bluethooth version of the eQ-3 are less than £10 so for £130 you have control of each room.

Since there is no way to turn off the DHW when the CH runs I simply set my Nest thermostat schedule for DHW in winter to off, and I have loads of hot water in winter even when set off. In the summer I set Nest to run ½ hour a day and 1 hour on Saturday to stop legionnaires. I would guess we use around £600 worth of oil a year.

However first thing I did was get the boiler serviced, the jets wear, so over time it uses more and more oil, so annual service means either the pressures are set or jets changed so the meters used by the oil boiler service guy read the correct figures and since I have no intention of buying the meters, there is no point in working out what the reading should be, I pay around £140 and the boiler runs costing if anything less than I paid for gas in old house.

 

[Squuiid]

The trouble is that the only way for me to have the boiler come on is by using the Warmflow boiler thermostat (see image below). This connects to HW ON terminal 3. That is the only way to invoke the boiler as far as I can tell.
Terminal 4 (CH ON) connects to both Wilo pumps to push water out to the radiators only.

Is there a way to invoke the boiler for both HW ON and CH ON terminals using that single wire? I'm guessing not but I am no electrical engineer.

Also, if there is no DHW thermostat, as in your first C plan, you seem to imply that the boiler is always heating the water? Surely it doesn't come on unless the timer, in this case via terminal 3, tells it to?
I think I'm missing something in your explanation.

 

[hard-work]

Some things I do know, Drayton and EPH both do three zone stuff, this thread page one @hard-work has posted a Utube link on three zones with opentherm,

I think EPH goes up to six zones on Opentherm.

 

[ericmark]

If I am reading correctly you have no room thermostat? With new gas boilers the flame height varies (modulates) so no real need for a wall thermostat, although better with one, but with the oil boiler it only switches on/off, and you need some automated method of turning it off, the thermostat you show controls the temperature of the circulating water, it does not control room temperature.

There are two ways to control room temperature, one is with a thermostatic radiator valve (TRV) the other is a wall mounted thermostat, but because the boiler only turns on/off, using a TRV on its own will not work, as the boiler will keep cycling on/off even when not needed.

So we have a whole array of wall thermostats, for the price difference a programmable one makes sense, that means rather than setting the time on the programmer so either it heats home to set temperature or does not heat home, it has maybe 5 times and each time can have a different temperature set, so say 16°C when at work and over night, and 18°C drawing the day and 20°C in the evening. But although a hard wired one costs around £35, once you go wireless the cheaper ones tend not to fail safe.

So likely your best option is the likes of Hive, not a good thermostat, but likely good enough. But google programmable wireless thermostat and there are loads to select from, so to help you further what we need to know is a little about your families life style, including what you would like the control to do.

I use Nest, I will explain why I selected Nest, my son had Nest and said how good it was, living with my late mother I had problems controlling the central heating, so I bought Energenie MiHome TRV heads with the idea of adding Nest latter, when we moved here I brought the TRV heads with me, they were claimed to work with Nest, I also found the three wires that should have gone main house to flat below house with the boiler in some where changed colour and so only two worked, but I wanted three to work CH and DHW with most systems, but Nest could do it with two wires only and only 12 volt and since I don't know where it changes colour it seemed safer to use 12 volt. In other words it was not fitted because it has geofencing or occupancy detection, but now fitted I use it.

I hate the word "Smart" that's what my hand did after having the cane at school, but the problem is some of the systems are really smart, some times too smart for their own good, and turning the temperature up and down for a few weeks manually and it remembers what you like and auto sets a schedule for your heating, others "Smart" means it connects to your phone, and there is nothing really smart about them.

Much also depends on the house, my wall thermostat is in the hall, not ideal, but it is centre of the entrance floor of the house, the living room gets the sun, so with my house if the wall thermostat is in the living room, then rest of house can get rather cold, my last house was open plan, and one wall thermostat centre of house worked fine.

It takes time to warm up a house, I work within walking distance of the house, so using a car there is about 3 minutes from when the geofencing detects I have left work, to me getting home, so simple schedule works best, son lives 25 miles from work, for him geofencing works well, so before saying I think you should fit EPH thermostat we need to know your needs.

My dad lived with central heating like yours for years, in the morning before he got up it warmed the house, and at around 10 pm it warmed the house, in both cases around an hour, the idea was it heated bedroom before he retired for the night, and house before he got up, but in the day he used first coal, then went to coke, and finally gas fires, the central heating was only used to warm house while he lit the fire.

I think the previous owners of this house also used an open fire to burn wood, I am a lazy so and so, I want to forget the heating of the house, just want it warm, so never lit the open fire, just made a cover so I can put the AC exhaust up the chimney.

So try to explain your goals.

 

[hard-work]

If I am reading correctly you have no room thermostat? With new gas boilers the flame height varies (modulates) so no real need for a wall thermostat,

Eric you need to have a control interlock, to prevent boiler cycling. That may mean a wall thermostat, pipe stat or whatever. I know with some modern controls it may be a bit meaningless. A boiler can modulate down quite low on its boiler controls, but a small level of boiler cycling may occur. Some boilers have anti-cycle parameters to reduce all this effect. But you still need the interlock.

 

[ericmark]

@hard-work yes I know it still needs some method in the warmer weather to turn off a modulating boiler, but with anti-cycle software this could be human, turning it off with a switch.

But the boiler shown I do not think will modulate and unlikely to have any anti-cycle software, so unless he either only uses it until fires are lit, it will need some method to control the output, he has shown no wall thermostat or TRV, seems only control is temperature of circulating water.

I know there are many options, but can't see how one can advise without some idea of level of automatic control required, I know EvoHome will work, but EvoHome is not cheap, so was hoping I could work out what level is required, but he has to tell us, my crystal ball is not that good.

What I am looking for is a program of improvements he can make, starting with the TRV which does not need any wiring, but don't want to say fit cheap eQ-3 if the guy wants in the end to control it all from the phone.

I was told turning the thermo syphon off with a motorised valve will stress the boiler and reduce it's life, I am no plumber, or heating engineer, I did as I was told, I know with an integrated boiler and control system flame goes out, and boiler continues to run for a short time, so what I want and also I would think the poster of this thread is to know if you fit a motorised valve to turn off DHW will that damage the boiler?