VAILLANT DIAPHRAGM PUMP

[8aviashusband]

I'm toying with using a Vaillant 16-0108 pump for an application which is nothing at all to do with a Vaillant boiler ('cos I can get one cheap). As the pump is listed as a spare for several boilers, I scoured this site to try to find out exactly what it does in these boilers. If I knew, it might help to confirm (or not) its suitability for my intended use.
Can someone familiar with these boilers please advise? - or does anyone know where I can find the spec for the pump?

 

[Gasguru]

It creates a very small air pressure to drive the gas valve.

You won't find a spec anywhere since it's custom made part by Vaillant.

Don't pay more than a couple of quid...they are a very reliable part and there are few boilers left that still use it...ie virtually zero demand.

I suppose you could use it for a fish tank.

 

[8aviashusband]

Thanks for the info, Gasguru.
It looks as if this pump was never intended to pump water, so its not going to be useful in my application. (which was in a kind of DHW secondary circulation system with one outlet, to get 'instant' solar pre-heated water from a UV cylinder to a remote combi [via a Grant Combisol valve arrangement]. Pump would of course need all the features of a Grundfoss bronze bodied pump, except the £ sign.)

 

[Deleted member 105431]

what a ridiculous scenario.


best leave plumbing to the professionals.

 

[scatmanjohn]

Thanks for the info, Gasguru.
It looks as if this pump was never intended to pump water, so its not going to be useful in my application. (which was in a kind of DHW secondary circulation system with one outlet, to get 'instant' solar pre-heated water from a UV cylinder to a remote combi [via a Grant Combisol valve arrangement]. Pump would of course need all the features of a Grundfoss bronze bodied pump, except the £ sign.)

Explain why you would want to do such a thing.

 

[8aviashusband]

Ridiculous? Explain why?: Here's the history/reasoning:
We deliberately chose a combi capable of taking preheated water to replace our ageing (and leaking) oil fired boiler and LP HW system. The preheated water would be from a [new UV] cylinder heated (using its primary coil) by solar panels. To utilise preheated water, an arrangement of thermostaic valves is used (Grant Combisol, or simliar). If the preheated water is hot enough, it goes straight to DHW. If not, it goes via the combi. Ideally, the preheated water source needs to be close to the Combisol, otherwise you get big slugs of cold water affecting the way the system operates. In my case, I can't get the cylinder close to the boiler/valves. Hence the secondary loop idea. I don't want to waste water either, since we're on a meter.
Its quite possible in the south of England to get all DHW heated by solar collectors in the summer months, and a helpful contribution to running costs during the winter.

 

[mogget]

What's the maximum water inlet temperature for the combi?

 

[8aviashusband]

Not declared by the manufacturers in their Installation & servicing instructions, but as they make a Solar diverter valve (similar to Combisol) for use with this boiler, that diverts Solar heated water straight to DHW at 60 deg C, but into the boiler if its less, it would seem that it would accept at least 59 deg C.

 

[mogget]

A possible solution then - install thermostatic mixing valve near boiler. Preheated water from the unvented cylinder goes into the hot side, and mains cold water goes into the cold side. Then the output of the TMV goes to the dhw inlet on the boiler, output temperature limit set to 55 degrees.

This way, the combi will heat straight away and you'll get hot water quickly at your taps. As the hot water comes through from the cylinder, the boiler will modulate down, to a very low level if the cylinder is hot enough. If the water from the cylinder is more than 55 degrees, the TMV will add a little cold to protect the boiler.

You will still use some gas (oil?), even though the cylinder is hot. However you won't be having to feed the pump / controls with electricity. It's a simple low tech solution that will achieve what you want - that the heat in the cylinder is used in preference of fuel.

 

[Deleted member 105431]

ridiculous trying to use a boiler air pump that regulates gas pressure to circulate hot water.

 

[mickyg]

yep, a pump which creates a few millibars of pressure, perfect for the job

 

[mogget]

ridiculous trying to use a boiler air pump that regulates gas pressure to circulate hot water.

Yes, I've got to agree with that.

 

[mickyg]

Pump would of course need all the features of a Grundfoss bronze bodied pump

you need a bronze pump, there isn't a suitable alternative, thats why its a bronze pump. You don't want to buy one because of cost and yet your investing in a combi, an unvented cylinder and solar panels

 

[mogget]

... bronze pump...

I'd have thought that, with solar hot water, the insulation on the hot water circuit would have to be substantial. I wonder if the cost of running the pump, along with the heat loss from the pipe, might wipe out the savings gained from using the sun?

 

[mickyg]

I wonder if the cost of running the pump, along with the heat loss from the pipe, might wipe out the savings gained from using the sun?

bit late for that, the savings have already been spent on the cylinder and panels