Addition of pump to Gravity HW system.

[securespark]

A client of my builder friend has a bog standard gravity HW and pumped CH set up, using free standing Baxi boiler.

Trouble is, the builder wants me to wire a pump into the HW, controlled by a cylinder stat, so that when the HW is up to temp., the stat switches the pump off.

The reason for this unorthodox solution is that the gravity fed HW is struggling to circulate.

Any comments?

 

[doitall]

Piece of cake

All you have to do is re-plumb the boiler to the cylinder as a fully pumped system, the amount of work depends on the boiler and where the cylinder and heating pipes start and finish.

 

[securespark]

And the wiring is straight-forward too?

As mentioned previously, his plan is to take a feed from the HW side of the programmer to a cylinder stat, then on to a pump in the flow or return of the HW circuit.

This will work? Is it a recognised method?

I am not terribly well up with CH wiring as you can tell..... It seems to work in my logic, anyway....

 

[doitall]

And the wiring is straight-forward too?

As mentioned previously, his plan is to take a feed from the HW side of the programmer to a cylinder stat, then on to a pump in the flow or return of the HW circuit.

This will work? Is it a recognised method?

I am not terribly well up with CH wiring as you can tell..... It seems to work in my logic, anyway....

No it wont.

You have to control the boiler as well the pump. do a quick search for Honneywell Y and S plans, and you will find the wiring dia

 

[ChrisR]

Yes it might! Depending how you define "IT"!

Have done things similar and it works, though detail and function would depend on the specific system, and what you're trying to achieve.
What (I think) you want is that when the "HW" is switched on, the circulation from the boiler is pumped.
The pipe from the boiler up to the top of the cylinder's primary inputs is often the route the vent takes, so you can't interrupt it, but you can put the pump in the return. That's usually the lower pipe.

There's no point pumping cold water round so put a pipe thermostat on that rising/vent/top pipe from the boiler. Also put a thermostat on the cylinder.

For just improving an existing system, take a wire from the HW ON at the programmer, which will be the same as the "on" at the boiler (if not then yell), through the pipe stat and the cylnder stat, to the pump.
So the pump only comes on
If there's a demand for HW
and if the primary pipe is hot
and if the cylinder isn't hot enough yet.

That's just one of several possibilities. If there's already a cylinder stat then you should be able to use the live feed to that. If there are no wires going to the airing cupd from the programmer/boiler you can still do it by getting power locally - on a timer if you want.
Note that the water will still get hot by gravity circulation whenever the boiler is on (ie when the heating is on) so doesn't satisfy building regs for a new system.

If you can get wires where you want, you can use a system like Honeywell A plan to turn the boiler off if the ch is off and the water's hot enough.

if you want a modern system do what DIA says!

 

[securespark]

To clear up any confusion, this is what the builder wants to achieve:

The system is currently a gravity HW and pumped CH system. Very basic.

BUT the gravity HW is struggling by gravity alone, so he intends to fit a pump in the flow or return to improve HW circulation. This pump will be controlled by a cylinder stat fed from the HW on terminal in the programmer, so when the water is up to temp., the pump switches off.

He also intends to change the current vent system to a manual vent.

Hope this helps.

 

[doitall]

As I said no, I would not advise it unless you re-pipe the boiler.

The vent must stay open to atmosphere.

 

[Bylough]

I have the same system with an Ideal Standard boiler, and it does not permit pumping 'cold' water in the primery system. Cast iron may crack I suppose in certain circumstances. Suppose you could get away with delayed pumping- is that what you mean?

 

[doitall]

No bylough thats not what he means

 

[kevplumb]

He also intends to change the current vent system to a manual vent.

somebody tell me this is a wind up pleeeeese

failing that why not just build a bomb and be done with it

 

[securespark]

No, it's not a wind-up. I know naff-all about plumbing, so am only reporting what I have been told.

Kev - what would you do to solve the problem of a gravity-fed HW system not flowing well?

 

[kevplumb]

as you have already been told marra by my learned freind s plan of y plan

there is a way round it BUT !!!!

 

[bradleybear]

Fit an electric immersion heater?
Save the hassle of not knowing what he's doing and drop an imeersion in?

 

[ChrisR]

securespark. I have answered your question. But you have asked the same question again. If you don't understand the answer, show it to your builder who will. Lots of people have done it, not just me!
In fact what's being created is not far off a standard two-pump system.

DIA on what grounds are you objecting?

Be careful if the builder wants to SEAL the system - the boiler may not permit that, then to do it would be dangerous. Call Baxi.

 

[doitall]

Trouble is, the builder wants me to wire a pump into the HW, controlled by a cylinder stat, so that when the HW is up to temp., the stat switches the pump off.

I am not terribly well up with CH wiring as you can tell

He also intends to change the current vent system to a manual vent.

Be careful if the builder wants to SEAL the system - the boiler may not permit that, then to do it would be dangerous

Chris Any good plumber should know the answer and how to do it.

In this case we have a sparkie with no experience of CH wiring, trying to find out how to alter a boiler layout for a builder friend who knows nothing about heating systems.

All you have to do is re-plumb the boiler to the cylinder as a fully pumped system

I'm trained to recognise danger and dangerous situation that is why I say get someone in that knows how to do the alterations