Should a boiler be able to turn on a pump?

ghelyar · Jun 9, 2018

I recently had a new hot water cylinder installed and changed from a y-plan to an s-plan. The plumber installed the cylinder, valves etc and left me to do the wiring.

The existing wiring was not great. The boiler is an old Potterton Netaheat Profile 50e. I wired the orange from the 2 valves, the live to the pump and the switched live to the boiler together in the junction box, and also wired the boiler into the permanent live (to reproduce what was previously there).

However, even with the programmer disconnected, my boiler can put power on the switched live and turn on the pump, presumably with both valves closed.

Should it be doing this?

I disconnected the permanent live from the boiler and it still seems to work with just a switched live when both the programmer and thermostat are on, but I don't know if I'm doing anything wrong by doing this.

Octopus · Jun 9, 2018

My advice to you is employ somebody to do this for you unless you are totally familiar with heating control wiring

ghelyar · Jun 9, 2018

Thanks, I'll take that advice under consideration. Stock answers aside, does anyone have any answers to the questions I asked in my post?

Octopus · Jun 9, 2018

ghelyar said:
Thanks, I'll take that advice under consideration. Stock answers aside, does anyone have any answers to the questions I asked in my post?

That's not going to help is it

How many central heating systems have you wired?

suffolkspark · Jun 9, 2018

Boilers can override any programmer instruction to run a pump for instance if a frost stat is installed, or for an over run, then they just pump round a bypass...

If you've followed an S-plan in conjunction with wiring instructions in the boiler manual then you should have no problems? If you are not competent to do that get somebody that is.

ghelyar · Jun 9, 2018

Thanks, suffolkspark.

I followed the wiring instructions and I'm confident that the wiring that I've done by the hot water cylinder is correct, it's just that I did not touch the boiler (and I'm not a gas engineer so I'm not going to) so I wanted to check the expected behaviour, particularly as I've read that some old boilers don't need a permanent live.

I didn't think it would be a frost stat turning it on in the summer, and I didn't think overrun would turn itself on out of the blue even with the programmer disconnected. I'll probably replace the boiler soon anyway as it's so old, loud and inefficient.

If the boiler puts power on its switched live connection to turn the pump on but the valves are not powered, would that mean it's trying to pump towards closed valves, or would they be open when unpowered? I thought they would be closed when unpowered, so only turning the pump on without opening the valves would not be useful, and may even damage the pump.

suffolkspark · Jun 9, 2018

ok well gas do usually have an over run after you switch them off but yes to start out of the blue doesn't sound right, without test equipment to find out where this feed is originating though your not going to find out.

they usually pump around a bypass during over run so the the valves being closed doesn't mtter

ghelyar · Jun 9, 2018

Thanks suffolkspark,

I'll reconnect the permanent live so that the overrun continues to work and get a new boiler installed.

buzzlightyear · Jun 9, 2018

[ElectriciansForums.net] Should a boiler be able to turn on a pump?

follower the yellow brick road Dorothy.

ghelyar · Jun 9, 2018

Thanks, but I'm already following the wiring diagram, and this one doesn't show permanent vs switched live on the boiler, or answer my question about the switched live on the boiler turning the pump on.

My questions have already been answered by suffolkspark so if the standard practise here is to close answered questions then please close this.

Sparkie30 · Jun 9, 2018

Maybe this will help

Good luck

ghelyar · Jun 9, 2018

Thanks!

Toneyz · Jun 9, 2018

I assume that the factory link between live and switched live has been removed. This boiler needs a live, neutral and earth supply a switched live from the oranges of the valves. you then have separate output terminals for the pump.

AJshep · Jun 9, 2018

Buzzlightyears diagram is spot on.
Most newer condensing boilers control the pump directly from the boiler, the pump overruns, to disperse heat.
Commercial and multiple boiler systems I worked with would have a shunt loop and pump plumbed into the system to have the same effect.

Wiring central heating systems incorrectly can be costly, if wired incorrectly it will reduce the working life of your boiler and void any manufacturers warranty.

Why the dislike for the first two replys which in my opinion is the correct advice ?

ghelyar · Jun 9, 2018

Because they don't answer the questions I asked. You could give the same "get someone else to do it" answer to any question, without even reading it. A bot could do this on any forum. I also thought the second post was quite rude and condescending, and did not add any value.

The better question is why did you dislike my posts? I was not impolite or unprofessional. I did not break any forum rules. I thanked them for their advice and asked for any answers to my questions, and I gave positive rep to the people who took the time to actually read what I asked and answer it.

Should a boiler be able to turn on a pump?

ghelyar

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Octopus

ghelyar

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Octopus

suffolkspark

ghelyar

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suffolkspark

ghelyar

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buzzlightyear

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ghelyar

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Sparkie30

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ghelyar

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Toneyz

AJshep

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ghelyar

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