Pump required on return from cylinder?

[EngineerJack]

a bit confused.

I have a boiler, which sends heat out via 2 valves / 2 pumps - one upstairs, one downstairs.
And also a hw send to the cylinder, a return from the cylinder with a pump on it. No valve one this one.

Problem is when the cylinder reaches temp, demand is stopped and the boiler stops central heating too. There is no zoning. All pumps are on or off.

So is it safe to disconnect the pump on the cylinder return and just use the immersion heater in the cylinder instead for Hw?

Or will the cylinder melt and explode.

The cylinder stat will still be connected and will still kill the boiler if temp is reached. So I can't see it running away.

Also, gravity fed open system.

All advice welcome.
Jack.

 

[Phill Peck]

Has it always done this?

Sounds as though it's just wired wrong

 

[ScottishGasMan]

So you have a pump for each heating zone, and a pump on the cylinder return? How big is this house?(number of radiators wise)

As above, definetly sounds like its wired wrong. theres no point doing as you say as you are correct the cylinder stat would sense the temperature and shut off heating - although you could remove the cylinder stat from the cylinder as the immersion heater will have its own thermostat built in.

But the cost to heat electrically may not be worth it considering it may be a relativley straight forward repair to get it going correctly.

As always, pictures say 1000 words if you have any

 

[EngineerJack]

So you have a pump for each heating zone, and a pump on the cylinder return? How big is this house?(number of radiators wise)

As above, definetly sounds like its wired wrong. theres no point doing as you say as you are correct the cylinder stat would sense the temperature and shut off heating - although you could remove the cylinder stat from the cylinder as the immersion heater will have its own thermostat built in.

But the cost to heat electrically may not be worth it considering it may be a relativley straight forward repair to get it going correctly.

As always, pictures say 1000 words if you have any

Yes a pump for upstairs, one for downstairs and one for HW return.
We have 8 rads downstairs, 6 upstairs. Single pipe open system.
Having had a look at the wiring, the timer, room stat and cylinder stat are all in series, so obviously if one shuts down they all go. In summer we will have the reverse issue of heating on when we need hot water.

Jack.

 

[EngineerJack]

also the boiler controls the pumps, for pump overrun, so I'm not sure if I can just have the one HW pump running when I need it or completely isolate it from the system, however, heat is still getting up to the cylinder from the boiler. immersion turned off.

 

[ScottishGasMan]

Make and model of boiler?

 

[EngineerJack]

Ideal logic+ 30

 

[Agile]

It seems seriously wrong and makes me wonder how this ever came about.

I would charge about £180 to £200 in my local area to rewire a heating system properly.

Tony

 

[Nige F]

Are there 3 separate pumps or a double combined pump and a separate one.

 

[Agile]

Makes me wonder if the cylinder is really heated by a pumped feed and not just gravity circulation.

Does the water reheat in about 30-60 minutes?

Tony

 

[EngineerJack]

Yes it seems so. And to about 50C too. There is a stat on the cylinder which will kill the boiler if it gets too hot.

My plumber told me the header tank would melt and leak if not pumped. However the pump makes it so much hotter, as it should. The pump is on the return.

 

[EngineerJack]

Or perhaps it was the header tank in the loft? That makes sense but that should be cold only.

 

[simond]

Cylinder would melt and explode! Is this an unvented cylinder?

 

[EngineerJack]

Vented. I'm probably wrong and I mean the header tank.

I've also had it checked over and it looks fine. The concerns would be with over pumping the hw, as opposed to my initial query of not pumping at all. It's gravity fed.


Thanks for all your help. I think I have my answer.