Any experience of the GS200 small ASHP?

[Jeremy Harris]

53 minutes ago, PeterStarck said:

No it wouldn't because I would only be drawing, in my example, 17.5l/s the remaining 32.5l/s would be coming from the external vent.

 

 

But that doesn't comply with building regs, does it?  17.5/s doesn't even meet the intermittent ventilation extract requirement for a utility room, the regs require that any non-continuous ventilation provide 30l/s for a utility room and 15l/s for a bathroom:

 

 

 

Two bathrooms and one utility room adds up to 60l/s, so the ~50l/s from this unit won't be enough, as I mentioned above, and an additional 10l/s of extract will be required from one of the rooms.  We can probably ignore this additional 10l/s of extract from the replacement air requirement, as it only needs to run for maybe 20 to 30 minutes, but that still leave the need to provide ~50l/s into the house for the few hours it takes to re-heat the cylinder.. 

 

The real issue is that there will need to be air vent(s) into the house with an equivalent area to a 160mm diameter hole.

 

 

[Gone West]

37 minutes ago, Jeremy Harris said:

But that doesn't comply with building regs, does it?  17.5/s doesn't even meet the intermittent ventilation extract requirement for a utility room, the regs require that any non-continuous ventilation provide 30l/s for a utility room and 15l/s for a bathroom:

Correct. If an older house has an existing ventilation system ie trickle vents and I add one of these units then I haven't found anything in Part F that indicates I have to update the ventilation levels. I therefore don't need to extract 50l/s from inside the house but can extract a proportion of that from inside the house and the remainder from outside the house. I will just be enhancing the existing ventilation system.

[Jeremy Harris]

Just now, PeterStarck said:

Correct. If an older house has an existing ventilation system ie trickle vents and I add one of these units then I haven't found anything in Part F that indicates I have to update the ventilation levels. I therefore don't need to extract 50l/s from inside the house but can extract a proportion of that from inside the house and the remainder from outside the house. I will just be enhancing the existing ventilation system.

 

 

In this case, there is a requirement to comply with building regs as it's a new build ( @Thedreamer's installation with this unit providing the extract from two bathrooms plus a utility room).

[Gone West]

2 hours ago, Jeremy Harris said:

 

 

In this case, there is a requirement to comply with building regs as it's a new build ( @Thedreamer's installation with this unit providing the extract from two bathrooms plus a utility room).

Yes I agree, that's why I said there was confusion because you were talking about @Thedreamer's build and I was talking more generally about the GS200 as was first discussed by the op. We got there in the end.

[Thedreamer]

These systems run in conjunction with an electric immersion so the recovery time will not be as long as mentioned earlier. The longer recovery time is based on just the heat pump working by itself and also using a cooler outside temperature.

 

Using some electricity to heat the water and a warmer air temperature is going to result in a much faster recovery time.

 

From reviewing the manual there is two fan speeds so perhaps we will go for a slower speed for long period, prehaps when we are out at work. This should result in the requirement for fresh air to be reduced.

 

Generally, I don’t rate the stand-alone ventilation systems in bathrooms. You can buy one that shifts x litres per second but pretty much every one I’ve ever had has not worked well, I always just open the window to get rid of the steamy air. Living in a windy climate we always have a breeze here.

 

This is an area where I can't see how a flat in central London and a croft house in the Highland can be compared under the regulations.

 

Overall my expectations for the system are cheap hot water for six to nine months of the year and in the winter I’m going to rely more on the dual immersion heater within the system and make use of the stove to heat the replaced cooler air in the house. Hopefully over the course of the year it should balance out.

 

I spoke with the building control about the system and no concerns were raised.

 

 

[Jeremy Harris]

Be interesting to see how you get on.  You will need to make sure that the build isn't at all airtight though, as all that extract air must be easily replaced with air from outside.   Trickle vents in the windows most probably won't be enough, and will probably be a bit noisy with the volume of air that will be drawn through them.

 

Building control should be fine as long as the extract rates in the regs are met.

[Gone West]

13 hours ago, Thedreamer said:

I spoke with the building control about the system and no concerns were raised.

It will be interesting to see how interested your BCO is in the ventilation calculations. Our BCO wasn't interested at all. We use the EASHP to heat our 180l DHW tank and as we never use that much hot water at a time the tank recovers quite quickly.

[Thedreamer]

Thanks @Jeremy Harris & @PeterStarck for your comments on this thread.

 

Peter I note from reviewing your blog that your system does MVHR and hot water. I've learned a lot from the forum, if the budget allowed I would have pushed for this when our design was being done. Looks like a good set-up.

 

I'll provide an update once the system is up and running.

 

One final question we have quite a few velux windows upstairs with trickle vents. 

 

In winter would opening the trickle vents upstairs rather than downstairs result in air movement in warmer upstairs air being pulled downstairs and then into the system.  

 

Sorry @DamonHD for moving away from your opening post.

[Gone West]

4 minutes ago, Thedreamer said:

In winter would opening the trickle vents upstairs rather than downstairs result in air movement in warmer upstairs air being pulled downstairs and then into the system.  

Yes there would be a degree of passive stack effect but how much would depend on the total area of the trickle vents. It would cause some probably noticeable draughts. We use passive stack ventilation in the summer to cool the house by opening the bathroom roof window. It can be very effective.

 

 Sorry re-read your post and the answer is no.

Edited February 25, 2020 by PeterStarck

[Thedreamer]

1 minute ago, PeterStarck said:

Yes there would be a degree of passive stack effect but how much would depend on the total area of the trickle vents. It would cause some probably noticeable draughts. We use passive stack ventilation in the summer to cool the house by opening the bathroom roof window. It can be very effective.

 

Ok thanks, reason being that I'm concerned that I might end up with the heat rising from our stove etc and the upstairs being hot and the downstairs being cold. 

 

Upstairs, we have 6 large veluxs, 2 smaller ones and a window on the gable end all with trickle vents.

 

I can heat the house with our stove although with the trickle vent this is going to be inefficient. But I can compensate for this inefficiently by using our endless amount of timber in our stove.  

[Gone West]

3 hours ago, Thedreamer said:

 

Ok thanks, reason being that I'm concerned that I might end up with the heat rising from our stove etc and the upstairs being hot and the downstairs being cold. 

 

Upstairs, we have 6 large veluxs, 2 smaller ones and a window on the gable end all with trickle vents.

 

I can heat the house with our stove although with the trickle vent this is going to be inefficient. But I can compensate for this inefficiently by using our endless amount of timber in our stove.  

There will be convection but some of the rising heat should be lost through the trickle vents in the windows upstairs so hopefully it won't be too hot. The problem is that trickle vents can be affected by the wind and it's difficult to know how effective they will be at any particular time. I wouldn't have thought that the ground floor will end up being cold though. It will probably mean tweaking the number of trickle vents that are open on both floors to obtain the best balance.