Which Boiler for Underfloor Heating

[Agile]

You need to calculate the whole house heating needs, probably about 10 kW in your case. Add 2 kW for heating a cylinder and a 12 kW boiler may well be adequate. But you have said nothing about the house or how many live there!

With UFH and a new build you can assume 100w per sq m.

With rads if you don't know any better you can guess at 1.0 kW per single panel and 2.0 kW for a double panel.

But an open pipe flow rate of 12 li/min is the wrong measurement and most likely to indicate an insufficient dynamic flow rate.

But rather than ask us why not ask your proposed boiler installer? That's assuming he will be someone competent to design heating systems.

Tony

 

[tomcio01]

Thanks Tony,

The reason I am pestering you guys for the info is because when I come to speak with the installer I want to have an idea of roughly what he should be proposing, to make sure he A). knows his stuff, B), is not taking me for a ride.

Anyway, it's a 3 bed semi with 8 rads. shower and bath upstairs.
the washing machine is on every other day (we have 2 little ones).

I am no expert and therefore with the information provided is there a boiler you could recommend to keep the house warm and the hot water flowing?

I mentioned the Veissmann Vitodens 100-W (35kW), would this do the job or is a combi out of the questing and I need to stick with a tank?

 

[Agile]

What year semi?

Solid or cavity walls?

What colour and material is the outside of your cylinder?

Based on your wrong type of water flow measurement I would say a combi is out of the question and retaining a stored hot water system is best. But the correct measurement in the correct place might give different results.

I have this possibly wrong idea that in less populated areas the heating engineers are more capable and do not rip anyone off. What town/village/city are you in?

Tony

 

[D_Hailsham]

As part of the extension work I uncovered the water main pipe and it looked like a 22mm; but it was lead.

I believe you can get lead pipes replaced for free. Check with your water supplier.

I'll have to check the main tap in the house and probably replace it as it's quite old anyway and may be restricting the flow.

I thought of that. It might not be fully open.

As I said before, the Whole house boiler calculator will tell you what size boiler you need if you have a HW tank.

Do it in two parts:

1. Original house, including HW allowance
2. Extension, without HW allowance

The extension should be treated as a semi-detached as one wall is connected to the existing house.

 

[Agile]

Only some areas replace lead pipes for free.

In London they now seem to add phosphoric acid to the water to passivate the lead instead.

Even where they do replace the lead its often subject to annual budgetary limits.

Tony