MHRV & What type of fire?

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zander

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We have installed a Mechanical Heat Recovery ventilation system in our new build and we are trying to choose our fire / stove now. We are getting different information from everybody and we don't know enough about it ourselves.

Room 1
Ideally we would like to use a double sided multi fuel or solid fuel stove in the kitchen but we have been told that we can't becuase when we open the door to re fuel that it will cause smoke to escape and there will be a smell of smoke all over the house.

What have other people used or if you have any advice we would appreciate it.

Thanks
 
We have MHRV and two wood-burning stoves - one an inset and the other free-standing.

We've never seen smoke escaping from the inset, whatever the setting on the HRV or the weather conditions.

On the free-standing stove, there is sometimes some localised escape of smoke and ash, but I think this is mainly because a) the burning is much more intense when you open the door and b) the draw on that chimney isn't as good.

We usually turn the HRV up to "medium" when the stoves are on, but experimentation has shown that this doesn't really make a difference to the smoke.

Bear in mind you'll probably have an HRV extract in the kitchen anyway. We find there's a slight smell of smoke for a few minutes but that's all.

SSE
 
All I can say is that we got our HRV system by an engineer who recommended a multi fuel stove and we also got a woodburning stove, so if the company who designed it didn't forsee this as a problem I don't know who will. As SSE said, perhaps a little smoke but sure an open fire does the same with wind down the chimney and the disappears in seconds. Usually if you have MHRV you have stoves.
 
Thanks for reply's. Just wondering what brand stoves / fire you have. We need ours to be double sided and the chimney is in the centre of the house not on an outside wall.

The company we got our HRV system from (paid 10k) are not very helpful, they are just saying we can use any gas or solid fuel fire that we want to use.
 
Sorry to hijack but hoping to put in MHRV too and was wondering if the people above had normal stoves or if they had supplied air to them via the chimney or pipe making them completely room sealed?
 
cowboy said:
Sorry to hijack but hoping to put in MHRV too and was wondering if the people above had normal stoves or if they had supplied air to them via the chimney or pipe making them completely room sealed?
Click to expand...

they should always be room sealed....

otherwise the affect the balance of the heat recovery system, causing issues such as described above, but ,more importantly, reducing the efficiency and possible making them more energy consuming that saving.

but even more importantly.....
[broken link removed]

the risk of fire spead with HRVs is REAL...... insist on dampers were the ducts pass thruogh construction... insist on a connection to fire detection systems to power off HRV systems in case of fire....
DO NOT let the sales people tell you it is not required!!!!
 
Our house is an airtight house hence getting the stoves in, we use one chimney but this is still airtight as the stoves stop air flowing in or out. On one side we have our sitting room and we have the multi fuel charnwood cove 2 which is good heat for our good sized sitting room so the retailer told us, and on the other side we have our living room which is the wood burning stove Bronpi 8kw. We got this as the living room will only be used on special occassions.

Sydthebeat, never heard of fire spread, we have metal ducting through the house, would this just relate to the plastic type version. Sorry can't open link, certain restrictions but I don't think we got dampers in. Risk or has it happened quite a bit?
 
Abbica said:
Our house is an airtight house hence getting the stoves in, we use one chimney but this is still airtight as the stoves stop air flowing in or out. On one side we have our sitting room and we have the multi fuel charnwood cove 2 which is good heat for our good sized sitting room so the retailer told us, and on the other side we have our living room which is the wood burning stove Bronpi 8kw. We got this as the living room will only be used on special occassions.

Sydthebeat, never heard of fire spread, we have metal ducting through the house, would this just relate to the plastic type version. Sorry can't open link, certain restrictions but I don't think we got dampers in. Risk or has it happened quite a bit?
Click to expand...

abbica, as MRHVs are a relatively new technology to ireland, we are behind on the consequences on using them.
The problems are two fold:
1. If a fire starts in a kitchen a MHRV system can add to the spread of smoke around a dwelling. As we know smoke kills.
2. The grill/vent outlets in ceilings are usually plastic type. These have very little fire resistance therefore compromise the fire resistance construction of the floor.

These outlets should be fitted with intumescent sleeves that work after 30-40 seconds... not 10-15 mins as some do...

as i said above, just because they are not required by any regulation (yet) certainly does not mean they should not be used.....
 
I am in the stove business and this is a common problem as room sealing stoves are rare but getting more common and are relativily expensive as they seem to be by the more designer stoves at present.
I have been on to several HRV companies regarding the conundrum. some have said install a pipe as close to the stove therefore minimising the effect in theory as the duct should feed the flue only when the stove is on when its off is another matter. some people have installed air bricks under the stove etc. another has said that depending on the size of the stove in one case 8 kw that the hrv was delivering enough fresh air ( some thousand cubic feet per hour) to drive that size of a stove as long as that room was under positive pressure.
Any comments syd? you seem to be pretty well informed on them.
Is there a one size fits all soloution to this problem?
 
SSE can you give me the names of the stoves you have used. I am being told that I can only use solid, multi or wood burning stoves that have an air supply from outside but I cannot find any double sided stove or fire on the market with this facility.
Thanks for all replies.
 
Zander
There is a company called ES THERM LTD which have a double sided stove its calld a turbostove also im nearly sure it can have ducted air supply to a turbine which controls the burning process. Ideal for your airtight house.
 
Hi Zander

They're both Nestor Martin, one inset and one free-standing.

When we were looking (2005/6) I couldn't find any stove with an external air supply.

We usually put the HRV to medium when the stoves are both on, and do a quick "boost" if smoke has escaped. Note that if you let the fire burn down to cinders then reload you get virtually no ash. If you load when there's still flames you get a snowstorm.

SSE
 
Hi SSE,

I just stumbled on this thread at the right time, we're looking for a fire insert at the mo and planning to install a HRV in a new build. Where did you get your nestor martin stoves?

Do I take it that the HRV will affect the supply of air to a stove or convection fire insert?
 
Hi - both from Stove People in New Ross. No connection with them.

I think the ideal situation is to have a separate air supply to the stove itself, making it truly room sealed and consistent with air tightness. As I said, I couldn't find any suitable stove with this feature - probably because the stoves work by throttling the air supply.

I guess as long as the HRV is providing positive pressure to the room where the stove is you should be OK, in our experience anyway. The HRV installers didn't raise any concerns (we actually have two smaller HRV units for the two sides of the house).

You do also have the option of adding a "supply pipe" close to the stove when it's on, I think some people are doing this nowadays. Not sure how you'd go about sealing it etc. when not is use.

Also make sure your HRV intakes are nowhere near the chimney!

SSE
 
Thanks very much for the info.

Will keep it in mind when purchasing and installing.
 
Hi all thanks for replies. I contached the company suggested above by Magtape and spoke to Eammon, he was really helpful and I think he has fires and stoves that will suit houses with HRV installed he is just checking out a few things for me, so thanks Magtape.
Basically I think you need the unit to take air from outside and most stoves don't allow for this.
 
Guys and gals a few brands to net search for external air supplly stoves.

Tonwerk , Rais ,Cera, Rika, Scan, Saey


Some i know can be sourced in ireland , some in uk.
 
Hi
We have just completed a pretty much air tight house and faced the same problems as yourself. We have an MEV system, no heat recovery but air extraction.
We went for the Hwam Monet stove, you can order a seperate pipe for a dedicated air supply for it that fits in a purpose inlet in the back . We have a seperate duct for this alone to supply air to the stove, the main part of the duct is plastic, but the few feet into the stove is corrugated metal. The stove looks great, the stove shop in Greystones supplies them although we are in the uk and sourced it here. Saw it in greystones in the first instance.
 
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