What are the drawbacks of the ACV Heatmaster?

[ringi]

I am thinking about a heating/dhw system for a HMO that will have many showers so need good hot water flow rates. As the tenants may wish to have different room temperatures, at times the heat load could be very low.

As I understand it, the ACV Heatmaster condenses very well while producing DHW and gives a good flow rate. Additionally being a high water content boiler, it is more forgiving to a low heat demand without having to have a radiator that is always on to act as heat dump loop or lots of cycling of a burner.

So apart from the size of the ACV Heatmaster, way is it not used more?
Are there more restrictions of where it can be sited then a normal boiler plus hot water tank?

 

[doitall]

1st question is whats the peak demand and where is the water coming from to satisfy it.

 

[ringi]

I wish I know the peak DHW demand!

There will be 5 rooms each with its own shower and 1 person living in each room. Clearly it is very unlikely that all 5 showers will be in use at the same time. It is also very likely that there will be times when more than 2 showers are in use, so a normal combi will not cope. (Therefore I expect a store of heat will be needed given the limits of a normal gas supply.)

I think it is reasonable to assume that a system has to cope with all 5 people having showers before work, so 5 showers within less than an hour would be a reasonable target. Hence recover time may be more important than peak flow rate unless the tank is very large.

I will not know the main water flow rates until after I have brought a property, however the properties in the area are on 20mm plastic main pipes and I have not heard of problems with flow rates.

I like the ACV heat master having large water content, as that allows a timed TRV in every room without a system becoming unstable due to only one room wanting heat. Very few boilers modulate down to below a few KW and that is more than the heat loss from a single room in spring or autumn.

Total heating demand does not seem to be an issue, a rough calc come out in the 15kw to 25kw range.

 

[compheat]

Very expensive piece of kit

 

[ringi]

I just phone ACV and got some prices.

About £2500 for the 25c and about £3500 for the 25tc.

The 25c includes the safety kit for DWH, but it is extra on the 25tc. 25TC condenses 100% of the time for DHW, but the 25c only condenses for heating. (25TC has a preheater for the incoming cold water that is round the outlet of the flue – a bit like the “gas saver” from Zenex)

Heatmaster boilers are not covered by BG under a service contract. (I like the option of a BG contact as I can blame BG if it takes a long time to get a problem fixed…)

So the 25t costs more than a Greenstar Highflow 550CDi or Vitodens 222-F but has the advantage of being a “forgiving” boiler as it has large water content. (A system boiler + mains DWH tank is a bit less depending on installation costs.)

The 25TC costing about £1000 more has the advantage of the lowest running costs for DHW apart from maybe the Alpha Flowsmart Gas Saver.

(However I can offset running and repair costs against income tax, but not capital costs.)

 

[Dean744PiN5]

Your unlikely to get the flow rate needed if you have a 20mm incoming main.
Even 3 showers running at say 10lpm need a flow rate of 30lpm plus if people flush toilets, run sinks ect whilst others are showering will all add to the load.
You could easily have the capacity to run all 5 at the same time by using a break tank and booster pump (such as the grundfos homebooster) giving 50lpm. And by putting flow restrictors/aerators on each outlet.