Cylinder Sizing question –. The “Domestic HW cylinder selection guide” was
developed from BS 6700. It uses the equations and minimum cylinder sizes from.
DECC Heat Pump Road Shows: FAQs February 2012
MCS Licensee Gemserv Limited 10 Fenchurch Street London EC3M 3BE Company Reg. No: 4419 878 Tel: Fax:
+44 (0) 20 7090 1082 +44 (0) 20 7090 1001
[email protected] www.gemserv.com
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1.
Background
Gemserv in its capacity as the MCS Licensee, completed activities to update and have the MIS 3005 standard ratified by the MCS Standards Management Group. The new standard MIS 3005 v3.0 was published in early September.
The MCS Certification Body Forum noted that the specific requirements in the new standard would be challenging for installation companies to implement. The Certification Body Forum advised DECC that a programme of training would be needed for the industry to up-skill and achieve compliance to the new standard.
Gemserv were awarded the contract by DECC to deliver a series of road show training events to accomplish this objective. Below is summary of the FAQs collected during the sessions.
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2.
Frequently Asked Questions
No
Question
Answer
1
Are there any requirements on grouting for
All boreholes should be grouted and this
boreholes?
recommendation is to be added into the guidance to go with MIS 3005
2
How do I ensure the power of the pump is
Power Pump > Pressure Drop (2.5% Clause
greater than the pressure drop?
4.2.18). Pressure from Ground Collector pump > Pressure loss Ground Collector loop + Pressure loss Heat Pump evaporator + Pressure loss in Header. Pressure loss from the evaporator and header are supplied by the manufacturer/supplier. Pressure loss in the collector loop is calculated using engineering mathematics.
Clause 4.3 now refers to HE Guide. How do I
The spreadsheet calculator now has Heat
use this info to calculate power, energy and
Emitter Guide default values built into it. All you
cost data?
need to do is enter the data into the Main Variables Table (or leave it as a default setting if you so choose) on the ASHP or GSHP worksheet and also confirm that you are OK with the blue italic default settings in the Hot Water Energy Calculation section and you can follow through on this worksheet how the HE Guide and other data is used to compute HW usage and other customer info.
Do I need to perform a room by room heat
A room by room heat loss calculation must be
loss calculation to quote?
completed and the customer informed at or before the contract to commence the work is signed. This does not preclude using a variety of business models for quoting and estimating; however, it does require that before the contract is signed, the customer must be made aware of the room-by-room heat loss of their property.
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Can I use an elemental heat loss calculator
BS EN 12831 requires an elemental Heat Loss
to perform my heat loss calculations?
Calculator (HLC) appropriate for building/application in question. If the building or HP application becomes more complex, so should the considerations on heat loss, e.g. CIBSE DHDG is a fabric and ventilation heat loss calculator that will adequately represent an existing property built before 2000. As the property becomes more complex, with either say very high levels of insulation or with large areas of south facing windows, extra elements such as thermal bridging or solar gains should be included in the calculation process. For another application such as a swimming pool, this would require a pool elemental HLC.
Cylinder Sizing question –
Occupancy definition instead of floor size
The “Domestic HW cylinder selection guide”
Page 17 of BS 6700 states that a typical
was developed from BS 6700. It uses the
property uses 35 to 45 litres of hot water per
equations and minimum cylinder sizes from
person per day. 45 litres per day will be the
Annex C of this standard. Either the
standard HW consumption rate unless other
installation company must use the minimum
action is taken (e.g. low volume baths, low flow
standards stated in this guide or develop their
shower heads, etc.) to reduce hot water
own guidance based on BS 6700 or BS EN
consumption. The hot water calculation is
806.
based on a 45 litre/person/day multiplied by a typical house occupancy of (number of bedrooms +1) which gives a typical occupancy for a British home. It is fully recognised that in reality, occupancy is very variable. However, as typical British homes change hands every 7 years, it is important to design for the property and not the current occupant. We are aware that some hot water heat loss calculations are based on floor area of the property. The MIS 3005 guidance uses an occupancy based model to provide a simple yet effective solution. It is noted that as long as the installation company can justify and explain the reason for their hot water system selection choices and the householder is satisfied with
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the final solution, then other models can be used. However, we would recommend caution as heat pump hot water systems typically have longer reheat times as compare to combustion technologies and so conservative design procedures should always be employed. What pressures are feasible to perform the
PE 100 will not burst at the test pressures as
EN 805 Pressure Test and is there a danger
recommended in the training which is > 7.5 bar
of the pipe bursting?
and up to 12 bar.
I cannot choose the correct plant size when
MCS is working with SAP software developers
designing for a new build, what do I do?
to allow the plant size to be entered correctly following the heat loss calculations performed in line with MIS 3005. Further information will be available shortly.
When using secondary heat sources at the
A bivalent or multivalent heating system must
request of the customer how do I size to
be on a single integrated control circuit and
100%?
cannot have any monoenergtic space heating above the geographical design temperature. An immersion heater can be used for hot water heating as long as the local building regulations and standards are taken into account. Local regulations normally require the lowest carbon heat source to provide the load and the supplementary heat to source to be used as a back-up.
The Householder can also have a wood stove or other manual heating system separate from the main heating system but any auxiliary heat sources can only be included in the mono-tomultivalent heating design load temperatures if they are automatically controlled by the integrated heating control circuit. All automatically controlled heat sources must be fully interlocked. Definitions to assist installers (taken from John Cantor Book): Monovalent = Heat pump heats the building alone, without help.
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Bivalent = Heat pump operates with support from an alternative heater Dual Mode = Control Function for a heat pump with alternative heating device. Bivalent parallel = Heat pump stops and alternative heater takes full heating load. Part-parallel = Heat pump can operate along with secondary heater to a certain limit, then it stops and the secondary heater takes over. Mono-energetic = This is a bivalent system where secondary heater is electric. Therefore there is only one energetic source: electricity. Bivalent point or dual-mode point = Outside temperature below which the back-up may be required. This setting is a parameter configured into the controller. How do we know what the walls are like in a
The only truly accurate method for evaluating a
property? – U Values
U-value is to take a core of the wall in question and then build up a measured U-value for the wall. However, in practice, this is obviously an unrealistic method. There are three clues I (David Matthews) use to evaluate U-values of walls and I would be pleased to hear other peoples thoughts on this process as I am sure there is much more knowledge I can acquire on this process. First of all, I look at the overall property and this gives me an estimate of the buildings age so I have a good idea whether I am looking at a Victorian house with Flemish bond brickwork and solid walls or whether I am looking at a later property with Stretcher bond brickwork and cavity walls. Cavity walls took off from the 1920s onwards. I check every wall separately as some houses mix solid and cavity walls. For example, solid walls on the front rooms and a cavity wall extension bolted to the back of the house. Secondly, I measure the wall thickness in the windows and doors to see if it’s a 9” solid wall
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to an 11” or 13” cavity wall. 9” walls indicate a single brick thickness across the across the wall as in the Flemish bond. The 11” walls are likely to be brick-cavity-brick and the 13” walls brick-cavity-block. Whilst measuring the wall thickness, you can also check whether the inner wall is plaster or plasterboard. Using table 6.1 of DHDG, you should now have a reasonable idea of wall type. Choose conservatively opting for the higher U-value unless you can demonstrate otherwise. If you have say a rendered outer wall covering e.g. pebbledash or a tile or timber clad wall, there is a greater range of wall types including timber frame all the way through to table 6.4 of DHDG. With this range of construction types and careful measurement, you should be able to make a reasonable fit to one of the wall types in the tables. Finally, if it’s a cavity wall, check for tell-tale drill holes that have been refilled with mortar that indicate cavity wall insulation. If there is no sign of cavity wall insulation and the owner has no evidence otherwise, except for houses built in the late 90s onwards, assume it’s an unfilled cavity wall construction. Please provide any feedback on the above through Gemserv to David Matthews. How do we make sure the property is
At some point we have to say over to you. If
correctly measured?
you use either a laser/digital measuring device or a tape measure, it’s really up to you to learn how to use it properly and carefully. If the tape measure is not free to touch both walls or the laser is not bouncing off a wall squarely, the result can be skewed and so inaccurate. I take internal dimensions and then add wall thicknesses as appropriate. Personally, I have always used a big tape measure. My colleague who was doing lots of surveys had a fairly
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expensive laser measuring device so as to considerably improve his productivity. And please be careful, it’s so easy to read the millimetres correctly and then read a 15 instead of 16 cm or a 5 rather than 6 m because you are focused on the smaller scale and so miss the bigger picture. I recently did something similar with a vernier. As we say, garbage in, garbage out. And always draw a sketch layout of the property so it’s easy to review the notes when you are back in the office. How do I cater for trace heating on
If possible, design the drain so that it doesn’t
condensate drains when performing a heat
require trace heating. If it’s a short, fat and
loss calculation?
potentially insulated pipe that runs vertically to drain, it shouldn’t need trace heating. If you do require trace heating, make sure it is linked into the controls so that it is only used when required e.g. freezing temperatures when the heat pump is in operation. Its energy consumption and so running cost must be stated separately as part of the paperwork to be signed for at contract stage as it’s, just like the central heating pump, a separate element in the design spec.
Will using SAP and adding in the
SAP is not a BS EN 12831 Heat Loss
supplementary details from the CIBSE
Calculator (HLC) because it doesn’t perform a
Environmental Design Guide A or the met
room-by-room calculation & isn’t geographical.
office data meet the requirements of the new
Therefore, it cannot be used in its current form.
MIS 3005?
However, if the methodology was adapted to make it regional & room-by-room & use data from CIBSE Guide A, then it would in all likelihood qualify as a 12831 HLC. However, we cannot guarantee this as it all comes down to the individual adaptation process & ensuring engineering rigour. Certification bodies are there to make sure rigour is followed.
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