Heating control question

Dtp1979

2 prog stats and standard flash timer for hot water. I Want the hot water to take priority when either heating zone is activated alongside the hot water.
The reason for this is because the heating operates with weather compensation. But when hw is activated the boiler overrides weather comp and turns up to 82 degrees to heat the cylinder as fast as possible. This is all fine once the HW is timed seperate to heating. But if they come on together the boiler fires at 82 and the rads become scalding hot.
Edit.. I want it so that when HW reaches 60 the heating will go back to weather comp mode.
Here's a basic layout. PL and Neutral omitted for clarity

Tuco88

Just a thought, I am probably taking this wrong.

Rads getting to hot at a particular point?

If so could you use a second pipe set point to energise a relay to bake both browns to the dedicated MVs?

So giving the rads a max temp without effecting the HW?

Dtp1979

Tuco88 wrote: »

Just a thought, I am probably taking this wrong.

Rads getting to hot at a particular point?

If so could you use a second pipe set point to energise a relay to bake both browns to the dedicated MVs?

So giving the rads a max temp without effecting the HW?

Not that, it's just they get too hot. If I turn on HW for 30 mins the both MV's open, both switched lives are activated on Boiler. But the boiler that it is will choose 82, so that means everything will heat to 82

Tuco88

Dtp1979 wrote: »

Not that, it's just they get too hot. If I turn on HW for 30 mins the both MV's open, both switched lives are activated on Boiler. But the boiler that it is will choose 82, so that means everything will heat to 82

If you use a second pipe stat set a let's say 60 degrees n/o, to bring on a relay to break the browns to the MVs for the heating zones effectively closing them while the HW valve and the boiler are on.

So you will have a max temp for the rads no more, not effecting the HW.

Like a temp high switch so to speak?

Is there not valve regulators you can get for rads to prevent them getting too hot?

Dtp1979

Tuco88 wrote: »

If you use a second pipe stat set a let's say 60 degrees n/o, to bring on a relay to break the browns to the MVs for the heating zones effectively closing them while the HW valve and the boiler are on.

So you will have a max temp for the rads no more, not effecting the HW.

Like a temp high switch so to speak?

Is there not valve regulators you can get for rads to prevent them getting too hot?

Not sure but the Boiier dictates the rad temp from an outside sensor so I don't want to mess with that

Dardania

Dealt with this problem before in a school years ago. We were still at design stage so could make some changes to rad sizes...but either way:
Do you need to flow at 82C? For legionella reasons, you just need to be above 60 (so say flow at 65C)?
How are the rads themselves controlled - the prgrammable stats or TRVs also? Is the issue that the rooms are overheating? Because the only impact really of the higher flow to the rads is that the rooms will heat up quicker...

Dtp1979

Dardania wrote: »

Dealt with this problem before in a school years ago. We were still at design stage so could make some changes to rad sizes...but either way:
Do you need to flow at 82C? For legionella reasons, you just need to be above 60 (so say flow at 65C)?
How are the rads themselves controlled - the prgrammable stats or TRVs also? Is the issue that the rooms are overheating? Because the only impact really of the higher flow to the rads is that the rooms will heat up quicker...

The boilers program dictates the flow to the rad based on the outside temp. It brings the rooms up to temp in the most efficient way.
The HW flow is 82 because it heats the water quicker

Dardania

Dtp1979 wrote: »

Dardania wrote: »

Dealt with this problem before in a school years ago. We were still at design stage so could make some changes to rad sizes...but either way:
Do you need to flow at 82C? For legionella reasons, you just need to be above 60 (so say flow at 65C)?
How are the rads themselves controlled - the prgrammable stats or TRVs also? Is the issue that the rooms are overheating? Because the only impact really of the higher flow to the rads is that the rooms will heat up quicker...

The boilers program dictates the flow to the rad based on the outside temp. It brings the rooms up to temp in the most efficient way.
The HW flow is 82 because it heats the water quicker

I understand. It also allow the boiler condense to extract heat from the flue gases.
With the HW, can you set that temp lower? Do you need it to be 82C? As, if you have a flash programmer on it, you can just run it longer to hit the setpoint (in the water)

Dtp1979

Dardania wrote: »

I understand. It also allow the boiler condense to extract heat from the flue gases.
With the HW, can you set that temp lower? Do you need it to be 82C? As, if you have a flash programmer on it, you can just run it longer to hit the setpoint (in the water)

Yes I can turn it down but the whole reason it's so high is for a quick reheat. Even more so now if I can run both together as that'll mean the heating won't be off for too long if I've to heat the water

ptogher14

Can be done relatively simple but you'll need to get someone with knowledge to have a good look at it. If the motorised valves are six wires valves you can wire the fire for the heating circuits through the valve for the hot water. Whether you use NO or NC will depend on if the valves are drive open or drive close. Another alternative is to feed the fire for the heating through a NC relay. Energise this relay with the fire for the hot water, (dropping out the heating).
Unless you are familiar with control circuits and understand the above get someone who does. The above might have to vary depending on the circuit. The circuit has to be planned out and double checked. Speaking from a sparks point of view 80% of sparks can't wire heating in a house. It always becomes a problem. So do your self a favour and get someone who can

Dtp1979

ptogher14 wrote: »

Can be done relatively simple but you'll need to get someone with knowledge to have a good look at it. If the motorised valves are six wires valves you can wire the fire for the heating circuits through the valve for the hot water. Whether you use NO or NC will depend on if the valves are drive open or drive close. Another alternative is to feed the fire for the heating through a NC relay. Energise this relay with the fire for the hot water, (dropping out the heating).
Unless you are familiar with control circuits and understand the above get someone who does. The above might have to vary depending on the circuit. The circuit has to be planned out and double checked. Speaking from a sparks point of view 80% of sparks can't wire heating in a house. It always becomes a problem. So do your self a favour and get someone who can

No disrespect to sparks but I don't actually know one in my own area that can do this. I wired the system myself. I wire all my own heating installs. Obviously this is a little outside the box for me, so hoping for a diagram from somebody here that knows if that's possible.

Skihunta13

Dtp1979 wrote: »

The boilers program dictates the flow to the rad based on the outside temp. It brings the rooms up to temp in the most efficient way.
The HW flow is 82 because it heats the water quicker

Try put a pipe stat on pipe feeding to heating valves( you may need two pipe stats, one for each mv).Break the cable going from mv to relay through the pipe stat. This should close the heating valves at a set temp.
Not too sure why you have 2 relay in your setup, is there not a grey and orange cable in each mv?

Dtp1979

Skihunta13 wrote: »

Try put a pipe stat on pipe feeding to heating valves( you may need two pipe stats, one for each mv).Break the cable going from mv to relay through the pipe stat. This should close the heating valves at a set temp.
Not too sure why you have 2 relay in your setup, is there not a grey and orange cable in each mv?

There is yes, I just wired it that way at the time

antoinolachtnai

An extra relay controlled on the HW side which will interrupt the CH while the HW is being called?

Your design idea is good but unfortunately your wiring is getting complicated. This is the problem with the traditional layout. The 'logic' of the system is spread all over the house. It is fine when it works but when anything breaks it is very confusing. This is why viessmann charge a few hundred extra for a boiler which condenses a lot of this complexity into the boiler I suppose.

Your boiler manufacturer's technical desk might be willing to help you with the wiring diagrams.

Dardania

antoinolachtnai wrote: »

An extra relay on the HW side which will interrupt the CH while the HW is being called?

Your design idea is good but unfortunately your wiring is getting complicated. This is the problem with the traditional layout. The 'logic' of the system is spread all over the house. It is fine when it works but when anything breaks it is very confusing. This is why viessmann charge a few hundred extra for a boiler which condenses a lot of this complexity into the boiler I suppose.

Your boiler manufacturer's technical desk might be willing to help you with the wiring diagrams.

Spot on - simplest approach to the problem, if the problem needs to be solved at all. And good flag of what issues could arise by solving the problem...

antoinolachtnai

Dardania wrote: »

Spot on - simplest approach to the problem, if the problem needs to be solved at all. And good flag of what issues could arise by solving the problem...

The problem actually does need to solved and not just by the OP. Weather compensation can save 2 percent on gas across the season and maybe more in this country with the volatility of the weather. At a national level that is an awful lot of gas and CO2. the only problem is the damned wiring. This is what makes the Viessmann (with its 4-pipe valve) pretty good value.

Dtp1979

antoinolachtnai wrote: »

An extra relay controlled on the HW side which will interrupt the CH while the HW is being called?

Your design idea is good but unfortunately your wiring is getting complicated. This is the problem with the traditional layout. The 'logic' of the system is spread all over the house. It is fine when it works but when anything breaks it is very confusing. This is why viessmann charge a few hundred extra for a boiler which condenses a lot of this complexity into the boiler I suppose.

Your boiler manufacturer's technical desk might be willing to help you with the wiring diagrams.

4 pipe wasn't an option for me unfortunately.
Would you mind sketching your idea of the extra relay?

Dardania

antoinolachtnai wrote: »

Dardania wrote: »

Spot on - simplest approach to the problem, if the problem needs to be solved at all. And good flag of what issues could arise by solving the problem...

The problem actually does need to solved and not just by the OP. Weather compensation can save 2 percent on gas across the season and maybe more in this country with the volatility of the weather. At a national level that is an awful lot of gas and CO2. the only problem is the damned wiring. This is what makes the Viessmann (with its 4-pipe valve) pretty good value.

for me, the simpler solution is to run the rads hotter while in HW mode - and just rely on whatever is controlling the room temp (be that TRVS or thermostat) to stop overheating.
The damned wiring is a real barrier to implementing controls. Any solution, to be rolled out country wide, has to be simple

antoinolachtnai

Dtp1979 wrote: »

4 pipe wasn't an option for me unfortunately.
Would you mind sketching your idea of the extra relay?

Will you have a look and see if this makes sense?

I have not tested it obviously but I think it will do the job.

ptogher14

It can be done, I've it done on my own system.

Without being a smart arse, do you know how the auxiliary on an MV works?

Might sound like a stupid question but a number of posts have mentioned pipe stats, clearly lads don't know how to use MV.

Check how many wires your HW MV has and if it's drive open or drive close

Dtp1979

ptogher14 wrote: »

It can be done, I've it done on my own system.

Without being a smart arse, do you know how the auxiliary on an MV works?

Might sound like a stupid question but a number of posts have mentioned pipe stats, clearly lads don't know how to use MV.

Check how many wires your HW MV has and if it's drive open or drive close

I do know yes. 90 percent of my installs are oil boiler with controls so I'm just used to having a switched live. That's why I didn't use orange/grey in the volt free connections. They're standard eph valves, normally closed with 5 wires

Dtp1979

antoinolachtnai wrote: »

Will you have a look and see if this makes sense?

I have not tested it obviously but I think it will do the job.

Thanks I'll have a closer look later

antoinolachtnai

Dtp1979 wrote: »

I do know yes. 90 percent of my installs are oil boiler with controls so I'm just used to having a switched live. That's why I didn't use orange/grey in the volt free connections. They're standard eph valves, normally closed with 5 wires

This isn't my business, but I think the OP has wired it the best way. Running volt-free out to the valve is certainly possible and reduces number of parts required, but is it really a good idea? It is fine when you know what you are doing, but what about the next guy who works on it (when the MV fails, probably). If he misunderstands anything there is a good chance he will fry the boiler.

antoinolachtnai

Dtp1979 wrote: »

Thanks I'll have a closer look later

Unfortunately my earlier diagram was too simplistic. It cut off the CH side of the boiler but didn't cut off the MV's which is the real problem. I think you need something like the attached. not too difficult if everything is close to boiler but might be tricky if the MVs are all in different places.

Further diagram below. Excuse the rubbing out.

If the stats weren't programmable cutting off power to the stats might be an option. Or using the auxiliary on the HW MV to control the power to the stats. Might still be possible depending on the wiring but is messy whatever way you do it.

Wearb

I just noticed this here on the elect forum. I had been discussing it on the P&H forum.

I think you are missing the point of the op's requirements (maybe I am). When his hot water is on he needs his rads to be controlled by the weather compensator. At the moment (if using heating only) the temperature of the water flowing in the heating circuit will vary with the outside temperature. He wants the rads to remain under this control when his hotwater is on at 82C. I cant see a way of doing that.

However if he wanted to control the max temperature (not variable) of the rads while the hotwater is on, then that would be a simple prospect.

@antoinolachtnai. Is your diagram only cutting off power to the heating MV's when the DHW is on, or am I misunderstanding it?

antoinolachtnai

That is it exactly as I understand it. He wants the HW to have priority over the CH.

This avoids two problems as I see it:

- radiators that are too hot

- the lukewarm water in the CH In warmish season 'stealing' heat from the hot cylinder.

Dtp1979

antoinolachtnai wrote: »

That is it exactly as I understand it. He wants the HW to have priority over the CH.

This avoids two problems as I see it:

- radiators that are too hot

- the lukewarm water in the CH In warmish season 'stealing' heat from the hot cylinder.

Yes I think you're second drawing will solve it.
So, if I have CH on, and then I turn on HW, this will close the heating motorised valves allowing the cylinder to heat up?
When the hot water is satisfied will it switch back to heating mode when HW reaches 60 or when the HW programmer is turned off? Either way is fine as it only takes 15mins to reheat my cylinder

Edit.. I see now, it won't matter as both effectively control the MV

Cerco

antoinolachtnai wrote: »

That is it exactly as I understand it. He wants the HW to have priority over the CH.

This avoids two problems as I see it:

- radiators that are too hot

- the lukewarm water in the CH In warmish season 'stealing' heat from the hot cylinder.

Just wondering how this will work when user wants heating and hot water? The relay seems to just switch out the boiler stats. Maybe I misunderstand?

I think at circuit diagram of the boiler controller would help to clarify the issue.

Dtp1979

Cerco wrote: »

Just wondering how this will work when user wants heating and hot water? The relay seems to just switch out the boiler stats. Maybe I misunderstand?

I think at circuit diagram of the boiler controller would help to clarify the issue.

As the reheat time for the cylinder is only 15mins, I won't actually require both to be on anyway.

antoinolachtnai

Dtp1979 wrote: »

Yes I think you're second drawing will solve it.
So, if I have CH on, and then I turn on HW, this will close the heating motorised valves allowing the cylinder to heat up?
When the hot water is satisfied will it switch back to heating mode when HW reaches 60 or when the HW programmer is turned off? Either way is fine as it only takes 15mins to reheat my cylinder

Edit.. I see now, it won't matter as both effectively control the MV

Yep, that's what is supposed to happen. When the HW goes on, yes, the relays should knock off the CH. When the HW is satisfied, the CH should come on again.

I have not done this myself, but I can't see why it wouldn't work.

This is basically what my Viessmann four-pipe does, i.e., HW priority. Less wiring though the wiring is by no means completely trivial with the Viessmann either!

Be interested to hear how it goes.

Tuco88

So its pretty much what I stated in post no4?

When your hot water gets satisfied @60 degrees and the MVs for the CH open again are you not left with the same problem of scalding hot rads still or is the programme sorting this?