ᐅ Is the heating system properly sized?

Created on: 19 Apr 2016 20:05
S
Schnail
Hello everyone,

We are about to decide which offer to choose from the heating installer!
As always, the quotes and sizing vary widely!!!

A few facts:

Annual primary energy demand targeted at 42.5 kWh/m²a (according to the latest calculation), which is 31.5% better than a new build.
The house will have about 240 m² (2,583 ft²) of heated space, including bedrooms, dressing rooms, hallways, and a basement party room (which will only be fully heated at certain times), so not all areas will be heated equally. In addition to the 240 m² (2,583 ft²), there are about 60 m² (646 ft²) of basement space.

Currently, 2 people are planned to live in the house, but up to 4 people maximum are expected 🙂

The most attractive offer is for a Vaillant flexoCOMPAKT VWF 88/4 with 8.9 kW, a 185 L (49 gallons) domestic hot water tank, and a 50 L (13 gallons) buffer tank.

On the other hand, I received an offer for a Buderus system with over 13 kW, a 390 L (103 gallons) hot water tank, and a 300 L (79 gallons) buffer tank.

We have a “normal” showering habit and rarely take baths, so very large amounts of very hot water are unlikely.

Every opinion counts, the order is to be placed on Friday.
S
Sebastian79
20 Apr 2016 07:32
Did you have the Vaillant system inspected and approved?
L
Legurit
20 Apr 2016 07:41
According to HB, yes... unfortunately, I wasn’t present for that. I also don’t know if it happened in person or over the phone.

The times I dealt with Vaillant customer service were not exactly highlights either... keyword "well" instead of "ground probe" and the heating load calculation (incorrect heat transfer value as the basis).
S
Sebastian79
20 Apr 2016 07:44
You should now have a sticker and a service booklet from Vaillant – the inspection is a requirement for the 5-year warranty.

You didn’t take advantage of Vaillant’s incentive program, did you?

Regarding the system layout: there are, of course, many variations, but a buffer tank was always included – either the much-disliked large one in the supply line or the safety buffer in the return line. However, this should not affect efficiency – it just costs a few euros (approximately 400 euros) and I had to agree to it due to the warranty conditions.
L
Legurit
20 Apr 2016 07:49
I’m following up on this... thanks for the tip.
S
Sebastian79
20 Apr 2016 07:51
The inspection must take place within 4 weeks after installation – at least that's what I understand.
L
Legurit
20 Apr 2016 07:57
I’m going to step on my builder’s toes here...