Re: Heating design diagram (preliminary)

You have a lot to learn.

I put the valve in because the UFH supplier has one shown on his manifold drawing. You're right about simply stopping the pump though... The mixing valve is thermostatic, so flow control should be via the pump.

Thanks, Aidan. For the benefit of The Wall, I've posted a revised drawing at

I can't see much which has been revised. Still lots to do to get it right.

It's posted at

This revised drawing reflected Aidan's comments. Whether my design is feasible is still open to discussion.

Do you mean that the weather compensator changes the boiler setpoint according to the outdoor temperature? If so, which (good quality) boilers have this feature, please?

For an inexpensive condensing boiler, if the resistance of the load is greater than the boiler pump's residual head, can I simply put an external pump in series with the flow output?

Yes.

The Veissmann you have been looking at. The MAN (Eco-Hometec). Cheaper is the Ferroli MaXima 35 S which incorporates a weather compensator and geared for UFH. A quick Google shows this for £625 + VAT, so well priced and a good boiler too.

The boilers with integrated weather compensators modulate the burner to suit.

Where did you get that from? Cheaper doesn't mean smaller.

Yes, but a boiler of around 25kw for your needs will do fine.

Your setup. If a boiler is only doing UFH, then no 3-way valve is required and the boiler is set to 55C max temp, and the weather compensator raises and lowers the boiler temp. Totally direct. Now a system boiler has an integral pump and will switch this off when the burner is switched off (there may be a run on for overheat). You want the pump on all the time. So a heating boiler that comes without a pump is probably the best option. The weather compensator switches the burner and the pump always running.

Some of the expensive boilers that take into account UFH may keep the pump running.

Thanks to everyone who contributed heating design ideas.

The design is finalised and I am considering placement of the components.

I plan to put the 40kW condensing boiler (Keston C40) and cylinder in a cupboard at one end of the bathroom. At the opposite end of the bathroom, 4m away, is the adjoining wall with my bedroom.

Is the boiler likely to keep me awake at night if I put it in this location?

Thanks to everyone who contributed heating design ideas.

The design is finalised and I am considering placement of the components.

I plan to put the 40kW condensing boiler (Keston C40) and cylinder in a cupboard at one end of the bathroom. At the opposite end of the bathroom, 4m away, is the adjoining wall with my bedroom.

Is the boiler likely to keep me awake at night if I put it in this location?

Make sure the cupboard is well sealed and flimsey. You make need draught stip on the doors to prevent sopunds getting oit. It does work.

Two Keston Celisus boilers are near the price of one 40kW Keston.

You've been quiet for the last few days. Been ill or ?

Leave him alone! Rarely is such lyrical prose posted here.. I love the idea of sopunds getting oit. ;o)

I've heard that the Keston boiler is noisier because the flue fan needs to go faster to get the air through a 2 inch flue. Any Keston owners out there care to comment?

Typo. should be..> Make sure the cupboard is well sealed and not flimsey. You make need draught strip on the doors to prevent sounds getting out. It does work.

I'm as right as rain. I have been abroad jet setting.

They are a bit on the noisy side.

This is similar to a system I installed a couple of years ago. with a 170L HWC and a Keston C40 (that's about 37kW output but runs at about 35kW due to service main inadequacy). It works fine. Except I used a 5-way S-plan and no UFH.

Since this is a sealed primary what does the 'top up' unit mean?

It's going to be quite some softener unit to process the flow that requires 28mm pipe 8-) Main Boiler flow and return should likely be 28mm even if only to the diverter valve and last return T. Most boilers of this size wil likely have 28mm/R1 connections. Cold: 22mm for the garden tap. Other wise it really is OTT.

Provided they leave and return in the same order. You have check valves to prevent back flow in the inactive zones. It might mean you need a higher pump setting for the farther zones.

Right off the boiler flow and return, suitably balanced against hogging all the flow.

I take it that you have an inadequate water main?

Bronze pump needed will (cost will equal total of all the other pumps). 8-(

As a Keston C25 owner and fitter of Keston systems I would say the C25 is nigh on inaudible. The C40 is less quiet and in retrospect I would fit 2x c25 in preference to one C40 - space permitting. However most of the time the C40 would be nowhere near full power, unlikely to operate at night, the noise seems mostly to come from harshness of the bigger burner fan.

I'm not sure how you would implement the controls to decide when to use the second boiler.

Those I have come across I would not describe as inaudible. Unless they were duffers. They were early units and Keston have done a lot to the Celsius since introduction.