First of all, I know nothing about UFH, never fitted, modified, repaired or specified it. I now need to quote for a combination boiler replacement and there are a few things that do not seem right about the existing setup and I need a bit of advice.
Currently there is a Worcester Bosch 350 combi that is running two UFH zones, each regulated by their own room stat but switched by the built-in programmer. The flow is hooked up to a 3-port valve with each port serving a manifold. One zone has an additional 15/50 pump. I do not recognise the 3PV, all I can say is that it has a large white plastic cover on it. The boiler has a direct rear flue and as far as I am aware, no new WB can be flued like this.
This is an ‘architect designed house’ i.e. testament to some knobends vanity and amongst its features is some tin cladding in a tear-drop shape that the flue exits from – not the sort of stuff that a few bricks and some sand and cement can be used on.
The lady of the house likes WB boilers and wants another one. I do have some room below the boiler to play around with, possibly 400mm or so. So, depending on the dimensions I may be able to drop the new boiler, reuse the hole and still have enough clearance underneath – I plan to check with WB technical later on.
So, onto my problems, hopefully someone can clear these up for me:-
Why is a secondary pump necessary? The house is not overly large. There are two manifolds each consisting of 4 loops.
I plan to specify two programmable stats for the 2 zones.
At the moment, the favoured boiler is the WB 42CDI. This I know will require volt-free switching so I cannot see how the 3PV is useful to me. I have no idea if the old boiler allowed 240V switching, but the new one certainly doesn’t. So, I would replace the 3PV with 2 zone valves which is fine, however if a secondary pump is required then how on earth am I supposed to fire this after its zone valve has opened? I need the volt-free switching from either valve to fire the boiler. All I can think of is to have the pump before the valve and having an auto bypass fitted and use the output from the room stat – but this doesn’t seem like an appropriate solution. What would be nice would be to have a relay switching 240V in response to whatever voltage the boiler is putting out and thus giving me the ability to use one of the zone valves to fire the pump, but I don’t know where to source something like this.
Anyway, hopefully this is a common problem and there is someone here able to point me in the right direction.
Oh, and finally I am going to offer the GW CX35 as an alternative boiler simply because it can have a direct rear flue – anyone know of any other decent alternatives?
TIA
Mike
Currently there is a Worcester Bosch 350 combi that is running two UFH zones, each regulated by their own room stat but switched by the built-in programmer. The flow is hooked up to a 3-port valve with each port serving a manifold. One zone has an additional 15/50 pump. I do not recognise the 3PV, all I can say is that it has a large white plastic cover on it. The boiler has a direct rear flue and as far as I am aware, no new WB can be flued like this.
This is an ‘architect designed house’ i.e. testament to some knobends vanity and amongst its features is some tin cladding in a tear-drop shape that the flue exits from – not the sort of stuff that a few bricks and some sand and cement can be used on.
The lady of the house likes WB boilers and wants another one. I do have some room below the boiler to play around with, possibly 400mm or so. So, depending on the dimensions I may be able to drop the new boiler, reuse the hole and still have enough clearance underneath – I plan to check with WB technical later on.
So, onto my problems, hopefully someone can clear these up for me:-
Why is a secondary pump necessary? The house is not overly large. There are two manifolds each consisting of 4 loops.
I plan to specify two programmable stats for the 2 zones.
At the moment, the favoured boiler is the WB 42CDI. This I know will require volt-free switching so I cannot see how the 3PV is useful to me. I have no idea if the old boiler allowed 240V switching, but the new one certainly doesn’t. So, I would replace the 3PV with 2 zone valves which is fine, however if a secondary pump is required then how on earth am I supposed to fire this after its zone valve has opened? I need the volt-free switching from either valve to fire the boiler. All I can think of is to have the pump before the valve and having an auto bypass fitted and use the output from the room stat – but this doesn’t seem like an appropriate solution. What would be nice would be to have a relay switching 240V in response to whatever voltage the boiler is putting out and thus giving me the ability to use one of the zone valves to fire the pump, but I don’t know where to source something like this.
Anyway, hopefully this is a common problem and there is someone here able to point me in the right direction.
Oh, and finally I am going to offer the GW CX35 as an alternative boiler simply because it can have a direct rear flue – anyone know of any other decent alternatives?
TIA
Mike
