Saturday 3 August 2013

Masonry Heater - 3

The system of free gas movement raised in my previous post has most notably been popularised by Igor Kuznestov and Alex Chernov who between them have many years of experience in designing and building heaters using this approach.

The "Masonry Heater Association of America (MHA)" website (1) has many examples of masonry stoves and at the 2008 MHA Annual Meeting featured a Double Bell Heater Workshop with both Igor Kuznetsov and Alex Chernov. From the photos and data sheets published from that workshop I realised that here was a heater that could potentionly  meet both my heating needs and, when finished with an appropriate surface, with the  house's concept.

MHA Double Bell Heater Design -  courtesy MHA

From the photographs presented and the dimensions given I was able to construct a scale model of the core construction to give me some measure of how the stove would fit within the overall scale of the large kitchen/dining/living space, approx. 6 x 12 m, in which it would be located. From the model I quickly realised that the scale and overall shape would be fine.

Scale model of MHA Double Bell Heater Design
(PS Sorry ran out of bricks!!)

Without further information being available - I was reluctant to purchase the plans for this and other heaters offered by the MHA - before I was sure it would meet the heating output I was seeking and in particular how it compared with the Missouri stove.

 It was then that I remembered a rule of thumb for calculating heater output quoted by Alex Chernov in his excellent paper "Masonry Heaters: Planning Guide for Architects, Home Designers and Builders" (2) that "1 sq.ft of heater surface will emit 185 BTU/hr under a 2 full loads/day firing schedule".

Using the core dimensions given for MHA workshop Double Bell Heater, with a facing of , say, 4-5inches thick, I have estimated the surface area to be approx.138 sq.ft

Therefore heater output for this design is 138 x 185  ie. approx. 25,000BTU's/hr.

Another view of the MHA Double Bell Heater - courtesy MHA

The alternative design considered, the Missouri stove, which is designed to heat a 1200-1500 sq.ft (i.e. 110-140 sq.m) house has, for the simple design presented in the paper (3) a surface area of approx
100-110 sq.ft  thus output for this design is, say, 105 x 185 ie. 19,500 BTU's/hr.

Given the higher estimated output of the MHA Double Bell design for only a marginal increase in building complexity and costs this seems the more appropriate choice for meeting my masonry stove heating requirement. In addition, and most importantly, with a suitable exterior finish it will be more readily adapted to the "industrial look" that I am seeking to create in my house.

(1)   Masonry Heater Association of America

(2)  Alex Chernov "Masonry Heaters: A Planning Guide....."

(3)  Missouri Designed Masonry Stove