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nod

By nod
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nod Advanced Member

nod

Posted
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Im at the stage were we are ready to install the UFH

Electrician is looking to get started in a few weeks

But I would like to have a plumbing and heating plan in place first

ive approached two heating company's one suggested one boiler for UFH the other for hot water

The second company totally different approach

Whats the best way forward?

Does BC have any say in what we use?

I did post a question regarding SAP no takers}

Should I consider SAP when deciding which way to go?

 

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nod Advanced Member

nod

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14 minutes ago, Nickfromwales said:

Two boilers is a bit ridiculous TBH, unless you have a swimming pool or a 12 bedroom 6 bathroom house? 

I thought that

The second guy just laughed

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PeterW Advanced Member

PeterW

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57 minutes ago, Nickfromwales said:

Two boilers is a bit ridiculous TBH, unless you have a swimming pool or a 12 bedroom 6 bathroom house? 

 

.... or unless you bought a few in that offer when PlumbCenter cleared them out and you're trying to find a home for them ..... 

 

I've seen that done - also seen a 30+Kw boiler in a 3 bed semi as the "heating engineer" was a boiler short of his target from the merchant to get his free week in Marbella ... 

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Nickfromwales Advanced Member

Nickfromwales

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British Gas boast that their 30si WB is for a large flat / small house so I doubt if that's a problem tbh. I used to fit the Baxi 105e and then 105He as "hi flow" combis and they were 30kw iirc, and is not fit a thing lower than 28kw if you have a bath, even in a  treehouse. :). 

7 minutes ago, MikeSharp01 said:

Hey... We are contemplating a 35Kw boiler in our passive house for on demand DHW so 30Kw does not sound our of line for a semi.:D

And hot water you'll get ;). Is that the Vaillant ?

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PeterW Advanced Member

PeterW

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9 minutes ago, MikeSharp01 said:

Yep. Looks like we will also have ASHP for UFH am working on how to make the UFH run from both sources. 

 

Explain ..?? Why not just use ASHP to run the UFH as it's going to be at near optimal CoP..?

 

If you really wanted you could just use a small hot water tank as a buffer and connect the coil to the boiler but leave the ASHP and UFH on the open tank volume. It would give you the ability to use both then. 

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Nickfromwales Advanced Member

Nickfromwales

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4 minutes ago, MikeSharp01 said:

Yep. Looks like we will also have ASHP for UFH am working on how to make the UFH run from both sources. 

That would be best achieved with a medium sized buffer tank, but have it switch out when the Ufh is served from the ashp so you don't get the associated buffer losses all of the time ;). All depends if the heating load is well matched to the ashp output, eg a larger ashp would still short cycle to some extent, but with one sized appropriately that would be reduced to a point where it was not an issue / design concern. Rom what I have read here and on EB though, it seems favourable to have a bigger than necessary ashp with a buffer and labour the HP far less with few / no defrost events. 

Others who stayed in college longer than me may be able to offer some further clarity on that as it not my forte. ( is that how you spell forte, or is it forté? ) :S

 

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MikeSharp01 Advanced Member

MikeSharp01

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10 hours ago, PeterW said:

Explain ..?? Why not just use ASHP to run the UFH as it's going to be at near optimal CoP..?

At the moment I am not sure, have not done the detailed work of calculating, of the economics (thermonomics) so I was keeping my options open to allow a system that could use either so it could choose at time of use which one to use depending upon the conditions / energy costs of each source at the time. The ASHP should do most of the work but there may be times when it cannot run at a high enough COP and the cost of gas gets under the curve and we use that. I don't like the buffer tank idea, because of the standing losses but provided the total heat output is used in the control calculation I am optimistic that it could be made to work. This not the least because I have a feeling that we will shortly be facing variable electricity pricing which could change the the thermonomics on a minute by minute basis. As things stand our design demand points are the UFH, DHW and an air heating battery in the MVHR system with PV, ASHP and Gas Combi as our prime movers, (me and my other half as the other, not so prime, movers) so getting these to all work cooperatively and optimally is the design goal I just need to work through the detail.

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Nickfromwales Advanced Member

Nickfromwales

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The air battery would deffo not be suitable for use with the gas boiler. That would, when run independently and used solely for space heating, even be a bit 'small' for the ashp. Sizing correctly here will be paramount, or fit a 'seasonal' buffer and all these issues disappear. 

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Jeremy Harris Advanced Member

Jeremy Harris

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31 minutes ago, Dudda said:

Sorry, what’s a seasonal buffer?

 

Not sure what Nick means, but the only seasonal buffers I've heard of have been a bit mixed in terms of their installed performance. 

 

I'm aware of one in Ireland that was sold as being able to store excess summer heat to keep the house warm in winter, but my understanding is that it didn't really work that well.  I have some photos of it somewhere, and it looked to be a bit of an expensive experiment, one that I think the client paid for..............

 

There's another that was in Passive House magazine a couple of years ago that was reportedly better.  That was a massive cylindrical water tank that formed the core of a large curved staircase.  I can't remember the volume, but it was many thousands of litres I think, and well-insulated.

 

I have doubts as to whether the concept of a seasonal buffer makes sense, economically, as the engineering costs seem very high for what is only a modest energy cost saving.

 

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Nickfromwales Advanced Member

Nickfromwales

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Seasonal is a 'nicks term' for a buffer that you can have come into play when using the gas boiler, but not when using the ashp. It could also be set to come into play when the heat battery in the mvhr is set to work. Can also provide a bit of stored, pv-generated excess energy for DHW preheat, but the latter wouldn't be the sole reason for fitting it, more a handy bi-product of fitting it to 'tame' the gas boiler. 

Again, a solution unique to the problem / remit. 

 

Edited to add : sorry for the bum steer, just typing whilst leaving the house :ph34r: 

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Ferdinand Advanced Member

Ferdinand

Posted
Posted (edited)
On 2017-5-22 at 09:19, Dudda said:

Sorry, what’s a seasonal buffer?

 

A father-in-law who visits for the winter?

 

*Gets coat*

 

bum steer

What is one of those, then?

 

Is that when Clarkson talks about feeling things through the seat of your pants?

 

Edited by Ferdinand
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